Personally I believe committing to a project and sticking through with it is the hardest part about game dev, that being said small, bite-sized goals help me the most; for instance I try to break down nearly everything into steps and checklists. Currently I'm working on my main menu for my game, I've got it broken down into many steps such as: main menu title art (this is broken down further into the animation, the actual art, the implementation into the engine, I could go on but hopefully you get the point). Make it feel like you're making progress!
Also, scope of your game: keep it small!! Don't get stuck just adding mechanics and then the scope gets HUGE cuz then you'll never finish and you'll just get discouraged.
Yavga has a good point with separating work and home as well. I can't add much to that point as I'm (almost) always thinking about my game / planning, whilst at my real-person job anyway.
And if you truly don't feel like working on your game, take a break! Nothing wrong with that.