Focus on a project that you love: one that you truly support and one that you truly believe in. If you're 100% devoted to a cause, it will be much easier to continue pushing on even when it is no longer "fun". Remind yourself why you started, what you have achieved along the way, and what you still hope to achieve. Then just work towards achieving your goals - no matter how big or how small. Once again, if you're completely devoted, you'll take pride in your gains and this should keep you motivated.