If I get rejected, what then?

If I told my martial arts instructor (I'm 18; he's 20) that I was attracted to him and he rejects me, what should I do? How should I approach him to tell him that I'm attracted if I do decide to tell him? I'm just trying to weigh my pros and cons. :) He's the only instructor in my area of this particular martial art, so if I do get rejected I'm afraid that I might have to give up what I love doing.