Rejection

Why is it that rejection is so difficult to accept? Others opinions hold so much weight sometimes. As though my idea of success is dependent on them.
Let me go into some details. I've been trying to find a gallery to show my art, and I've dabbled in a few local shows. I tend to find discouragement. And not only from the galleries themselves, but rather from friends and those I consider dear. I refuse to agree with them, that I'm not good enough.
But am I just setting myself up for only future failures and disappointments?
I think I've just made up my mind.
As much as I'd love to have my art shown in a gallery, I don't think it will ever happen. I'm just being realistic.
It's disheartening really.
But when you don't hit the mark, you don't hit the mark, and there's nothing you can do about it.