There's a great editorial by Greg Moody on velonews today about that little demon that tells you to quit; that you aren't good enough.
Now my level of riding is nowhere near what he is describing but it was so perfect.
Whether you are in competitive sports or just recreational, play music, create art of some kind, it doesn't matter we all Everyone experience this demon. First he might tell you that "giving up isn't all that big a deal. People do it all the time and the world continues to roll on its merry way through the universe".
Nothing matters except that at some point you give in.
If there is something that I am going to keep in mind though it is this:
"Somewhere in there, you've got to say no, talk back, drive the demon back outside your head"
This is how you succeed in whatever it is you want to do.