I think this is a perfectly legitimate question, and one we've all probably thought about at some point.
I can't say that I've worked in the field for long enough to have discovered a particular competitor as of yet, but that does not mean that I cannot be motivated by my future competitors. I've been told some version of the same magical list by many sources, including some on this forum:
There is always someone ...
- with a shorter drive to the gig than you
- who's willing to sleep less than you
- who knows more software than you
- who works quicker than you
- who's willing to work for less payment than you
Not the cheeriest messages, but they can be summed up in one sentence: You will always be a student in your craft. Kinda tames the idea of competition for me, at least psychologically.