This interview on Lifehacker with Ira Glass about how he does his work ends with a great piece of advice:

I’d just say to aspiring journalists or writers—who I meet a lot of—do it now. Don’t wait for permission to make something that’s interesting or amusing to you. Just do it now. Don’t wait. Find a story idea, start making it, give yourself a deadline, show it to people who’ll give you notes to make it better. Don’t wait till you’re older, or in some better job than you have now. Don’t wait for anything. Don’t wait till some magical story idea drops into your lap. That’s not where ideas come from. Go looking for an idea and it’ll show up. Begin now. Be a fucking soldier about it and be tough.

With some slight editing this could work for almost any line of work.