example: "Sprint 1 (2 weeks): get basic framework for game operational. Using placeholder art, prototype movement for game. Tasks: 1) render squares on the screen. 2) take user input and move squares 3) have basic collision detection to prevent sliding through ground"
if any of those tasks seems like it would take more than one hour / one sitting, break it down into subtasks
Then at a higher level, you can schedule "researching and prototype" sprints in between "develop core features" sprints and "bug fixing / refactoring" sprints
also, one thing I've found made a big difference is keep a "done" log every day as well as a "TODO list"
even if your "done" thing for the day was just "deleted 5 lines of unused code and removed a global variable" having it visible is good positive reinforcement
there's other tricks, like having a backlog of "10-minute" tasks for when you don't have enough time or motivation to work on something serious