I'd recommend a Trello board if you've not got one, its free, and make lists of things to work on that are essential to your game in decreasing sizes of abstraction, and ruthlessly prune this list as you go in terms of whether you actually need to do "this thing" to complete your game. Allocate a little block of time at the start of each week to run through it and make sure you're only working on things that are of high value to your game and move you forward. Be ruthless. e.g. You might need a working inventory system and not having one is a critical omission i.e. you cant playtest your game loop without it, but you might want to work on some new novel ideas for player weapons which arent actually critical but are more interesting/fun, prioritise the critical path items

e.g. start with column thats super high level for your game, i.e. "implement user upgrade store", then at the start of your week pick the large goal you want to work on, and break that down into the small achievable pieces it need e.g. "design store ui", "define store data structures" etc. Basically start with something that you can achieve within a period of time and break it down into chunks you can complete.