You can disappoint people and still be good enough. You can make mistakes and still be capable and talented. You can let people down and still be worthwhile and deserving of love. Everyone has disappointed someone they care about. Everyone messes up, lets people down and makes mistakes. Not because we are inadequate or fundamentally inept, but because we are imperfect and fundamentally human. But in God's eyes we are a perfect imperfection.Sometimes we just feel worthless when we realise we've messed up - sometimes our reactions to people who do mess up is completely unacceptable because we make them feel worthless.
Sin doesn't write you off from working on the mission of the church... if it did then none of us would be able to work on the Great Commission. Sin hinders our work yes, but Jesus' grace is greater - and it restores. Let's remember that we are restorers... not tearers down.