Found one? Great.
Here's the good news, you don't have to believe it anymore. Write it down on a scrap of paper and then I want you to open up your Bible and search for a Truth. Find a verse that refutes your lie and then write it under your lie.
Ready for the bad news?
Now that you have pinpointed the lie (or lies) you believe and you have found scriptural truth, you no longer have any excuses. When the devil comes and whispers in your ear that you aren't good enough or you're a failure or you're worthless, take Jesus's example and throw those scriptures back at the devil. Remind him that you are a child of the One True God. Remind him that God never called the qualified. Remind him that nothing is impossible with Jesus on your side. Remind him that Jesus died for you.
"For if any man is a hearer of the word and not a doer, he is like a man who looks intently at his natural face in a mirror. For he looks at himself and goes away and at once forgets what he is like. But the one who looks into the perfect law, the law of liberty, and perseveres, being no hearer who forgets but a doer who acts, he will be blessed in his doing."
James 1:23-25 ESV