My suggestion for motivation, is to work on your games when you're not feeling motivated. You may come up with an idea or hear some inspirational thing that makes you feel motivated, and that's great, but you won't get much done if you rely on that. You need to set goals, and work towards them even when you don't feel like it (but give yourself a break sometimes too).

The great thing is that when you work on a game and make some progress, that helps motivate you. And you come up with more ideas, which motivate you. So you may start the day feeling like you're just not in the mood to work, but you do it anyway and get motivated as you go.