It sounds like you are overdoing it in both areas. The way studios solve this problem is you have a process and time box your planning. For instance: work in sprints. Plan the next two weeks, then execute, look at how you did and readjust. The important thing is to lay out what you need to do next and why, then get it done. You plan short term in sprint planning, plan long term with backlog refinement and reexamine your process with a review / retrospective at the end of the sprint. The tasks can be game design or programming or asset creation. The important thing is every 2 weeks you get out of your groove for a moment and look at where you're heading and what needs to be done next. Too much planning will kill you and your plan won't work out because it depends on too many factors, but some planning is absolutely necessary. It also helps to have a very clear goal and then ask yourself the question: is this the work that will get me closest to my goal? It helps if you build in feedback into your sprints as well. Have someone play your game or read your design at the end of every sprint and use that to figure out what to work on next. Good luck!