The secret of concentration is elimination.
Do you have a "to don't" list? That's more important than your "to do" list. I don't allow anything to come in to something that I feel God has called me to do. So the secret is what you say no to.
I had a wonderful conversation with a guy I love like my son. He's developing, but he's got a lot of hangovers that he knows and I'm trying to help him with. And one day he said to me, "Prof, I can't believe what you do. How in the world do you do everything you do?"
I said, "You want to know?"
"Come on. Tell me."
"By not doing what you do."
So this guy's telling me about all the movies he saw, television programs, football games he attended. Wonderful things. I don't do most of that, not because I don't enjoy it, but because it keeps me from accomplishing what God has called me to do. And in order to do what you want to do in ministry, you're going to have to say no to all kinds of stuff that you enjoy doing. It'll be a test of your true commitment, your leadership.