In my life I have thought, wrote and believed those words thousands of times. But it does me no good. In fact, it makes me worse. I can wallow in self defeat, or I can do what I can when I can and be the one who gets back up, even though they're not upper half of the barrel and not the sharpest knife in the drawer.
I will probably do more good and be happier with the latter.
I hope you learn to love and accept yourself and understand that either no one is good enough, or everyone is.