Sometimes, it pays to say yes. As creative artists, we are always told that in order to grow with our art, we need to take risks; think "out of the box". It supposedly opens us up to new opportunity and experience.
That is absolutely correct. I find that if something scares me, it's more the reason to say yes to it. Now, I'm not talking about "extreme sports" or skydiving, bungee jumping, or things that might result in serious injury or death (to an untrained person). In those cases, fear is a good thing.
But fear is a good thing in your career as well. Sometimes it can point you in the right direction. We get so used to doing things the same way year after year, that the comfort ends up letting us grow stagnant like an isolated pond. Eventually the water goes bad, and so the same with our art.
Saying yes also requires that we are able to recognize bona-fide opportunities in order to capitalize on them. We don't always get that three-picture deal from Paramount, but sometimes we get an offer to work on a project that might or might not be something amazing. Usually these indie projects end up going nowhere, but sometimes, they actually launch into something very cool.
I recently had the opportunity to work with a director on a lead role in a short MMA-themed film. I also had the opportunity to choreograph the action. The director really liked my work and wanted to work with me. I looked at it as a way to really practice my craft, and an opportunity to try something a little different. It's very rare that an actor will get to collaborate to this extent, and so it can feel a little intimidating.
But if you've been working on your craft all along, it's time to trust that you can fly, and go ahead and say YES. It might just take you to the next level.