It is ours alone. We can do what we want to do. We can be who we want to be. Respect other people's opinions, but don't allow others to define who you are. If you base your self-image on others' approval, break the pattern.
Rejection is a part of life.
No one can make you feel inferior without your consent. One of the best guides I've read on attitude improvement is the classic The Power of Positive Thinking by Dr. Norman Vincent Peale. Motivation is fundamental to achievement in any field. As I have noted, it's far easier to generate motivation when your job interests you, calls on your strengths, and presents achievable challenges. But great achievers bring motivation to almost everything they do.