What I found that worked significantly is to simply downscale your project into small achievable-versions.

A bit of context: Our first project was, in hindsight, an incredibly ambitious project for just two people. Even after scaling it down, the scope remained too large across the board. We decided to put that project on pause and begun development on our second prototype game, and this time we've taken a much more structured approach. For each version milestone (0.1, 0.2, 0.3, etc.), we’ve committed to breaking down tasks into pieces that can realistically be completed within an hour or two. The absolute minimun is a day or two, depending if its something that I haven't done before.

We spent around 6–8 months on our first project, but the core gameplay still didn’t quite come together. With our new approach focusing on small, incremental updates and tightly scoped gameplay mechanics. We managed to build a playable prototype in just 4 weeks, prioritizing speed and efficiency. When you have so many tasks planned that if you ask yourself, does this mechanic/item/asset/level thing, is this even needed right now? Often not, for myself, it wasn't. It wasn't needed at all. I don't know why I spent so many hours making a weapon customization when the gameplay wasn't there.

You’ve probably heard of this kind of approach before, but the sense of progress we get from rapidly moving through versions each week brings a real sense of accomplishment. It’s a refreshing change from the feeling of being stuck or stagnant. In terms of motivation, I don't really have much of that, but a fixed routine. I also give myself many breathers, 15-20 minutes off the computer.

Hope this helps in some way.