One of the tendencies I've noticed about myself is that I tend to perpetually daydream but never actually act on anything (maybe this is an INFJ thing?). So I fear sometimes that my daydreams will stay just that... daydreams... forever, instead of actually being realized. I think my stepping out of my comfort zone and actually going back to school is a huge step of actualization though, as will moving 1000 miles away to Los Angeles (something about a change in scenery makes everything seem more real).
I'm not really sure if this qualifies as something that I'm afraid of, but it was still an interesting thing to think about, and it gave me something to write today! ;)