When you're in college, you're in your own little microcosm, very much like a repertory company. When you graduate from college, however, you are on your own. It's good to have confidence in your abilities, but you must be prepared to be humble and take the small roles. You have to know when to be a spear-carrier and when to turn it down. If you're fresh out of school, it would probably be in your best interest to take whatever comes along, but when you get more established, you need to be willing to turn things down if they don't further your career.
All actors face rejection.
All actors audition a lot and don't get jobs. It is more important than anything else that you learn to put it in perspective. There are only so many jobs, and you can be the best actor that walks into the audition on a given day. That does not mean you will walk out with a job. Don't let that get to you.