"We learn wisdom from failure much more than success. We often discover what we will do, by finding out what we will not do."
Samuel Smiles
Expanding as a human being is where we find our satisfactory moments.  When you do something that you aren't sure that you can do and fail, it gives you another opportunity to go back and try again with the new information that you've learned.  When you do something that you aren't sure that you can do and succeed, then you celebrate and find something else to do that makes you feel unsure.