If you see swarms of guys coming around you, you have to try and avoid being stuck on the kerb.
Hollywood is fickle; your career can end pretty fast. If the acting jobs dry up, you have to have something to fall back on. In fact, that would be my advice to kids interested in acting - make sure you get an education too.
I think with any sort of rejection, you're angry that you weren't enough for that person.

