itch.io

If you're still experiencing confusion, I've found that this video is a good step-by-step tutorial on how to get everything set up, especially if you already have project files. GitHub Desktop is a good beginner tool for using GitHub, especially with Unity. If you're working solo, don't worry about branching all that much. It's a handy thing to know how to do but if you're not worried about working on multiple features at once or working with other developers, its ok to leave it along for now.

My only real warning is keep an eye out for file size. GitHub has an individual file size cap, but if you're keeping most textures at about 2k or smaller, you should be fine (biggest culprits). If a push fails due to too many files (it'll pop up an error like connection timeout), just split the commit into parts and it'll work eventually.

If you end up being more interested in GitHub and how to use it more effectively and the tools at your disposal when issues arise, these two games are pretty good teaching tools.

Personally, I have a task list or task board (there are a number of ways to do it, a lot of development uses Kanban or Agile methods). I'll usually then sort them by priority and complexity (think length of time, difficulty). Usually this helps with having a strict list on what needs to get done and prevents me from adding anything to a project unless I feel it is ABSOLUTELY for the benefit of the final product. 

I also have reasonably strict working hours for myself and try my best to keep to those. I am pretty well known for not being great at it. I definitely still deal with "my brain won't shut off and stop thinking about it" and then I'll usually pick up a small task and complete that or chip away at something larger.  I know some people use Pomodoro timers to essentially force themselves to take breaks or swap tasks. Most websites and tools that have them will allow you to select your own work vs. break time ratio.

While I'm not a games generalist, I do frequently split into different "departments" of game production, which I find can help with passion burnout for me. I'll split days or weeks into time I'm going to focus on art, programming, etc. If I find myself growing dissatisfied with what I'm working on, I'll try and wrap it up ASAP (whether that be finishing the task or marking what is left) and then swap to something else.

Is it perfect? No. Does it work for me? Most of the time.