This is a good question to ask yourself. Or at least it can be if handled correctly.
One doesn't want to unduly dwell on fears, but by identifying fears one can choose how to respond to them, rather than just reacting.
What do I mean by this?
If you are stuck in a situation and fear is blocking you from taking some course of action that you know you desire, then you need to think through and understand what you face.
While not all fears are unfounded or inflated, more often than not it is possible to see
1. that the outcome we fear is not as bad as we fear
2. that the outcome we fear is less likely than we fear
3. that the fear is warranted given the potential positive outcome--you can't win if you don't play. Some risk is justified.
Recognizing any of these three can help one look at the problem in a different light, and by looking at it right educe or eliminate the anxiety creating the block enough to move forward.
It's no good to dwell on one's fears--it's much better to focus on positive outcomes and how to create them, but by facing one's fears, they can be put in their place. It's not that one should be without fear, only that one should not be needlessly blocked by unnecessary fear.
A person feared that her committee chair would decide not to work with her. This was impeding her ability to do any work and to do more than apologize for her limitations.
But the chair had never given any sign of an inclination to do so. And professors, by and large, would rather have their students finish than not.
Beyond that, however, one can see that entertaining the fear does not help the situation: it prevents exactly the sort of action that would mitigate the situation. To the extent that the fear interferes with concentration, thus hampering research and creativity, it is itself an obstacle.
Instead of dwelling on the fear, one focuses on the courses of action that are most likely to bring about a positive outcome.
Sometimes people's fears are completely unjustified. For example, fear of using or citing the work of a professor with whom you work. I find this one surprising, but I've met more than one person with this fear. I suppose one might fear looking like a flatterer or sycophant?
As a general rule, if you are using work sincerely, because of your interest in it and understanding of it, this can hardly be the case. After all, the professor in question is supposed to be teaching you something, so it makes the greatest sense in the world that you would refer to that person's work as a model or as a foundational authority.
Anyway, while one doesn't want to get lost dwelling on fears, it can be productive to ask: "What are you afraid of?"