I've come to terms with the fact that I'm never going to have enough time in life to do everything I want to do. And I'm okay with that—I always have something on the list that I feel is worth doing, so it's hard to lose a sense of purpose.
When I'm overwhelmed with must-dos (rather than just want-to-dos), I try to remind myself that I just need to be doing something. It might not be the perfectly optimal thing to be doing at that particular time (though often it is), but it is indisputably better than paralysis.