Have you ever compare yourself to your church-mates? Thinking you're better than him/her or she is better than you in singing/teaching Sunday School students/playing instruments or in any ministry that you have right now?
I hope not! But if yes, I do understand you but please stop thinking that she is more effective than you or you are not that effective in the ministry that you have.
"We do not dare to classify or compare ourselves with some who commend themselves. When they measure themselves by themselves and compare themselves with themselves, they are not wise." (2 Corinthians 10:12 NIV)
The bible said it is not wise to compare yourself . Remember that we're NOT doing our ministry for our own or to please other people. We should seek God's commendation and avoid comparing.
As long as you're true to yourself, and you're doing everything for God's glory you'll find joy and contentment in your heart.
I pray that you'll be free and that God will fill your heart with joy in serving Him. That you'll never compare yourself to others because in God's eyes we are all His precious children.