I take it you are interested in becoming a phlebotomist? Taking blood is a relatively simple matter; but some people are much better at it than others. As long as you pay attention in school, and truly care about the comfort and well-being of your patients, you will do fine.
Are you doing the drawing or giving the blood? I f you're having it drawn, it's no big deal. It doesn't really hurt, just a pinch. Getting an IV put in hurts. Any time I've had an IV put in, it's made me dizzy and sick. But giving blood for a test or donation is a snap.