Who you are before you perform
The gospel names you first: beloved, adopted, made new. Work, failure, and other people's opinions are loud, but they are not the first word.
Reflection
You are not loved because you are useful. In Christ you are useful because you are loved. Read that again when the inner critic starts its sermon.
Practice. When you catch yourself ranking your worth, say out loud: 'I am a child of God.' Then do the next small task.