Every priest struggles with the awareness of his own sinfulness, especially when considering the awesomeness of saying the words of consecration during Holy Mass or giving absolution. Don’t worry. None of us is worthy of this.
It is the Lord who makes us worthy. Humility then, is the all-important quality, because if Jesus wants you to do this, if He is calling you, He will give you abundant graces to fulfill the call, including that great gift of humility.