As for long projects, I allow myself a generous ebb and flow. For HOME GAME 1, as a sort of experiment I said, "I'm going to work on a game all month", did so, and then stopped.
For HOME GAME 2 I spent a number of months developing it out of events which were unfolding in my life. The game sequences came to reflect my daily experiences, and I was not only swamped and stressed but so low on "ideas" that I had to keep waiting for new things to happen to me before I could come up with the next story beat. It was a clear example of turning life experiences into story, but it was happening in real-time, not in hindsight. I wasn't sure how it would end because it was ongoing...but it did end, and I finished the game/moved.
At my new HOME I drew a map of the space and said I would spend the next few years developing something epic out of it, and herein time finally slowed down some. I had experiences to draw upon and ideas in stock, but no rush. There was currently no impending disaster in my life, so eventually production slowed and I variously spent a lot of time not working on the game at all. I played through a bunch of exciting and ambitious games in the meantime, and gave much thought to how I could scale my own game up. All of a sudden, some of the more grand ideas seemed much more within reach.
Eventually trials caught up to me again and I felt fairly certain HOME GAME 3 was shoehorned into a fixed BAD ENDING, which was depressing. The game took a backseat until I could reorient my life again. Eventually I was able to channel those newest events into the game, pushing it through to the conclusion and cementing the possibility of a good ending. I didnt want to have to actually "invent" a good ending! By striving for believability, I find I'm sometimes left feeling unimaginative; I need to see or experience something myself, to convey it to others. I couldnt just imagine a good ending.
I think if you have stories to tell, finding the time to develop them has to be based around your lived day. If youre too busy to work on a project, then it will take a backseat, but thats not a bad thing, since you return with more fuel for the creative fire.
For me, notebooks become a portable world-of-the-project, and my notes absolutely helped me keep the ideas in order, the scale intact and the details manageable. I tried to always be jotting things into the notebooks, even if I hadnt touched the project itself in months. My phone was also used for many additional notes, and I eventually found some of them quite surprising since I had over time forgotten many decent ideas.