Why are we so stupid?

Sometimes I wonder what leads me to do the things that I do. I wonder how we can without thinking be so inhuman, so threatening, so out of control. I wonder if thinking realy changes this? I wonder how our being claimed by God as the children of the Kingdom, co-inheritors with Jesus Christ, and still do the stupid things that we do. Yes we as Lutherans believe we are simutaniouly Sinner and Saint. So we can be claimed and named by God and yet still be sinners, still do stupid things to our brothers and sisters. I struggle with this though. I struggle with my own sinfulness, my own humanness. I struggle with this in trying to understand how I can be called to be a leader of the church if I am so sinful. I struggle with how God could us me.
I know that God uses all of us, even those who may not believe in God. I can not put God in a box and say he can not have effect on anything or anyone. Or that we all are effected through others by God. I am this day struggling with how I can be a called leader and live in my sinfulness.
I struggle with this know that I can do all things through Jesus Christ who gives me strength. Yet I wonder where that strength is at when I act out in my sinfulness. Where is the strenght to live in the glory of God when I lash out in my sinfulness? God never leaves me, so how can I possibly lash out in sinful nature and still be with God? How do I live in this dichotomy, and continue to be able to be a leader in this church?
We are all leaders in the church, we are all gifted, we are all children of the same heavenly father. I am struggling this day with my place in this kingdom, I am stuglling with how his love can still be with me, through the lashing and sinful things I have done.