You're not a failure. I always beat myself up over the fact that I am awful at all things math-related. I feel like since I have a D in math, I am a complete failure at life (thankfully, I changed math classes and I have an A now). Nonetheless, I brought myself down because I wasn't good at that one thing.. and many others.
Satan often uses our weaknesses against us to make us feel like we're nothing. He's really good at making our God look like a hurtful God instead of a creative one. I am also not good at sports or taking criticism, but does that make me any less of a Christian? God doesn't use our weaknesses against us, He takes them and uses them to show us that we're great at something else. Your abilities and flaws are not what define you -- what defines you is how you live for Christ, and the ways that you glorify Him.
I just recently finished reading a book called Popular by Tindell Baldwin (which by the way, I highly recommend you read). One of the things she said was "I don't care what the world has told you about who you are and what you bring to the table, the King of the world calls you beautiful and full of wisdom. What greater compliment is there?" I mean is that truth or what? You are made who you are by the gifts God has given you, and those gifts are what He is wanting you to use to expand His kingdom. Why would He expect something out of you that He didn't create you to give? He made everybody with different qualities. Otherwise, wouldn't the world be such a boring place?
The great Hillsong United sings this song called "Broken Vessels," and I think the lyrics are so beautifully written: "You take our failure, You take our weakness, You set Your treasure in jars of clay, so take this heart Lord, I'll be your vessel, the world to see Your love in me." God wants you to show the world the ways that you sparkle. You are an exceptional creation, my darling. Don't let the lies from this world, or the voice from the one who lives below it, black out the many features that make you so incredibly loved.
I can't tell you how much God loves you just the way that you are. When you bring yourself down about the things you're not good at, you're insulting the Man who created you with a million and a half other incredible qualities. So, the next time you see that girl who is great at pitching a softball, remind yourself of the way that you throw around love to others like Jesus does.