One of the mistakes that we make is that we manage our work and forget about managing our careers. We do as we're told, we do it well, but we are controlled by choices made for us, based on what needs get done. We forget or neglect to make strategic choices of our own, that will further our careers. So we end up drifting from one necessary duty to the next without an overall vision of our own to guide us.
While we should be open to doing the difficult and unappealing but necessary things, whenever we can, we should also make our choices based on what is good for us.
So, I have two pieces of advice:
Don't be shy or fearful about jumping at an opportunity that is good for you.
Don't also allow too many choices to be made for you, or else you'll end up floating from one thing to the next without a clear direction or focus.
A teacher of mine from grad school used to say, "Don't do donkey work." He referred to work that was work for its own sake. If you're going to do work, let it build up to something that is a priority for you. Make every effort count towards your goal.