Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God.
Self-confidence, in the respect that I can do anything because I am good, is not a scriptural thought. God-confidence because Christ gives me just what I need to use for Him and His glory is the way our confidence should be. It’s not in ourselves but in God. He’s the source that gives the gift and the power to get things done - we’re not. Jesus is the One who died to purge away our sin - we didn’t. Christ rose from the dead the third day - we didn’t. Let’s be certain that others see that our confidence is really confidence in God and that I, as a person, have no confidence in myself.