Here's some feedback I gave elsewhere on these forums to manage your time... This might prevent you from not completing your game and suffering from scope creep.
One thing to be wary of is stagnating, its possible you will get tired of doing the same thing with little or no results. I'd recommend also scheduling, but also using a WBS (Work Breakdown Structure).
List your tasks along with subtasks into manageable time blocks. Then you can try and schedule those blocks when you know time will be available.
As a simple example, a high score table.
Many will just list "-Create High Score Table"
This you can breakdown into:
-Create High Score Table
1) Get graphic assets for display 2hr
2) Get font for display 1hr
3) Prototype display layout 2h
4) Write save score event 1h
5) Write Load score event 1h
6) Write display score event (*MILESTONE) 2h
7) Clean up display prototype 2h
8) Source audio 1h
9) Add audio 1h
10) Test 1h
11) Fix/Test cycle 2h
12) High Score Table complete
So, some will say you dont need the detail, but if you only have an hour, go get assets. You can then keep track as to what task you are up to which will make continuing easier.
Plan it out, sketch some levels, talk to friends for their input.