The only reason you feel threatened by rejection is the belief that acceptance can do something for you. So, the only reason you care about what people think of you is because you believe that their judgment can either hurt you or save you, neither of which is true.
It's important to let go of other people's good opinions in order to become free of the influence of their negative opinions. Which does not mean that you become insensitive or arrogant; you simply recognize that opinions are fleeting and relatively insubstantial, both the good and the bad.
When you're dealing with a polarity like that, you can only have freedom from the negative side by relinquishing desire for the positive one. Can't have one side of the coin without the other, etc.
I recommend
What do you care what other people think? by Richard Feynman, and also his other book
Surely you're joking, mr. Feynman