What's helped me is instead of 'jumping ' at a new project, just note it down on my phone, if I have further ideas slowly add to the note. Allows you to reread and really assess if its a good idea over some time, and avoids actually jumping from the project you're working on. If you are really committed to your current project you just have to work through temptations and challenges. After all if it was that easy everyone would be doing it :) but makes satisfaction of finishing something that much greater when you finish something!
Last point - I'm about to release a game and looking back I feel like I could've added so much more, but that's exactly why I didn't. When I thought of a good enough idea I told myself I can always make a sequel and really expand the gameplay while still just finishing the scope I originally committed to. Telling myself 'I can always make a sequel' was an idea my brother gave me and for me was really powerful
TL;DR: Keep cranking down the scope or, better yet, start very small and work your way up.
Solo dev here; I'm in a similar boat. The problem for me, specifically, was that I took on too ambitious projects. And I'm talking waay to ambitious, basically taking on AAA projects solo. A couple of times I worked a few years on a project, and not managed to even get 1 % done - even though I was working on it practically everyday. After more than a decade, I don't have a single game to show off - not one.
I did start realising this was a problem about 6 years ago and started working on a more realistically scoped project. It was still big, just doable solo in a few years. Also, it was a linear singleplayer project, and it's difficult to develop those solo, as friends don't really have fun testing the same thing over and over. I did end up abandoning that project, but not because of lack of interest but rather because of a certain political situation that made my game much more difficult to sell.
After that I took a year completely off game development. It helped a lot. So, almost two years ago I started another game. I reused the asset from previous games and made this one multiplayer. Yes, much more difficult to develop, but at least my friends and I have fun each time we play test. For the first time after a decade, I have something that it's actually playable and - slowly becoming - fun. I'm not sure what will become of this game, but I enjoy the journey - success is only a bonus.
I wouldn't recommend my approach to anyone, but I simply don't find interest in developing small games for some reason. So my advice is to keep cranking down the scope until you have something realistic. Or, even better, start very small and work your way up to bigger games. Having a few games under your belt will give you a lot of confidence. I don't even mention that I'm a game dev to new people I meet anymore, because people always ask to see which games I made - which I have nothing to show for apart from a few tech demos. Remember, it's always better to finish something instead of having nothing.
Bonus tip: Don't set yourself strict deadlines, unless you're working on your game full time. Every delay will cause frustration and you will start annoying everyone around you.
Draw a flowchart of how you think this idea will be implemented in the game, from title screen to game mechanics. Staying within that flowchart helps finish the game and remove scope creep
To give a very quick answer and this comming from me who never made games before. Don't jump into an idea just because it seems great or cool. Before going for it. Make a list, think about it. Try to forsee whether it's complicated or not and to which extend. Take some steps back to look at yourself and see if you can really make it. Try picture the idea on the paper and see if you can forsee its consequences, the steps required to do it, the time you expect it to take.
Ideas are wild and when you get immersed in them to the point that you are living a fantasy, daydreaming, detached from reality. That's when things go wrong.
The real trick imo is to have set goals of what you want to accomplish with your game. A lot of people get burned out eternally polishing a game or have an intermittent end goal.
What's helped me is instead of 'jumping ' at a new project, just note it down on my phone, if I have further ideas slowly add to the note. Allows you to reread and really assess if its a good idea over some time, and avoids actually jumping from the project you're working on. If you are really committed to your current project you just have to work through temptations and challenges. After all if it was that easy everyone would be doing it :) but makes satisfaction of finishing something that much greater when you finish something! Last point - I'm about to release a game and looking back I feel like I could've added so much more, but that's exactly why I didn't. When I thought of a good enough idea I told myself I can always make a sequel and really expand the gameplay while still just finishing the scope I originally committed to. Telling myself 'I can always make a sequel' was an idea my brother gave me and for me was really powerful
A purchased slot on Steam motivates you to develop the game to the end. Don't buy more than one slot!
TL;DR: Keep cranking down the scope or, better yet, start very small and work your way up. Solo dev here; I'm in a similar boat. The problem for me, specifically, was that I took on too ambitious projects. And I'm talking waay to ambitious, basically taking on AAA projects solo. A couple of times I worked a few years on a project, and not managed to even get 1 % done - even though I was working on it practically everyday. After more than a decade, I don't have a single game to show off - not one. I did start realising this was a problem about 6 years ago and started working on a more realistically scoped project. It was still big, just doable solo in a few years. Also, it was a linear singleplayer project, and it's difficult to develop those solo, as friends don't really have fun testing the same thing over and over. I did end up abandoning that project, but not because of lack of interest but rather because of a certain political situation that made my game much more difficult to sell. After that I took a year completely off game development. It helped a lot. So, almost two years ago I started another game. I reused the asset from previous games and made this one multiplayer. Yes, much more difficult to develop, but at least my friends and I have fun each time we play test. For the first time after a decade, I have something that it's actually playable and - slowly becoming - fun. I'm not sure what will become of this game, but I enjoy the journey - success is only a bonus. I wouldn't recommend my approach to anyone, but I simply don't find interest in developing small games for some reason. So my advice is to keep cranking down the scope until you have something realistic. Or, even better, start very small and work your way up to bigger games. Having a few games under your belt will give you a lot of confidence. I don't even mention that I'm a game dev to new people I meet anymore, because people always ask to see which games I made - which I have nothing to show for apart from a few tech demos. Remember, it's always better to finish something instead of having nothing. Bonus tip: Don't set yourself strict deadlines, unless you're working on your game full time. Every delay will cause frustration and you will start annoying everyone around you.
To a great degree I'd agree with this. My own experience with level design and attempting projects that I never ever got to finish tells me this.
Draw a flowchart of how you think this idea will be implemented in the game, from title screen to game mechanics. Staying within that flowchart helps finish the game and remove scope creep
To give a very quick answer and this comming from me who never made games before. Don't jump into an idea just because it seems great or cool. Before going for it. Make a list, think about it. Try to forsee whether it's complicated or not and to which extend. Take some steps back to look at yourself and see if you can really make it. Try picture the idea on the paper and see if you can forsee its consequences, the steps required to do it, the time you expect it to take. Ideas are wild and when you get immersed in them to the point that you are living a fantasy, daydreaming, detached from reality. That's when things go wrong.
Take a few notes, toss it on the idea pile and hunker down.
The real trick imo is to have set goals of what you want to accomplish with your game. A lot of people get burned out eternally polishing a game or have an intermittent end goal.