Okay first a less noble means of inspiration for me . . . Over the years I've seen a number of books, movies, roleplaying games and board games come out that included ideas I had long since came up with on my own but couldn't get to the market due to finances, time, etc. Each time it happened, it told me two things: I was on the right path and should have acted faster. That frustration has been one of my motivators, inspiring me to work harder.
When I was a kid I started dreaming up two universes that were linked in some ways (The Cosmoverse and Toonaria). Great comic books, movies and novels in the genres I love inspired me to further explore my own universes, and my enthusiasm hasn't waned after all these years. Absorb what you love and let it carry you and inspire you to bigger and better things!