Sometimes I hear this being said “Nobody is indispensable” and it seems like there’s a great deal of truth in there. It always follows with a “God can find another person to do this” kind of a reason behind it. While God can always raise up anybody to take your place, God has a even better reason why He chose you to be in that position in the first place.
Don’t use it as an excuse to quit. If you are in a particular place and position, God has placed you there and until God asks you to go, He has a specific plan and purpose for you to be there. Do your best and live your fullest potential when you are in that position. Honour what God has given you and in that you honour God.
Don’t use it as an excuse that you are not good enough. You are a child of God, created in His image. You have been given grace and mercy by God and God’s strength is made perfect in your weaknesses. You are valuable in that Jesus has given His life to redeem you. There is nothing more sacred in the life that you have and we have to value our lives because of who God created us to be and what Jesus did for us.