Mark 9, 33-34

[33]But when Jesus turned and looked at his disciples he rebuked Peter. "Out of my sight, Satan!" he said. "You do not have in the mind the things of God, but the things of men." [34] Then he called the crowd to him along with his disciples and said: "If anyone would come after me, he must deny himself and take up his cross and follow me..."

I read "things of men" to mean concerns of death (to be more specific doubting there is an afterlife, because there is no God) and other earthy matters. I read “he must deny himself” to mean to serve God a person must putout of his mind desires and focus on “things of God” and not believe it is acceptable to give themselves leeway for failure (falling short in competition of task or not being completely devoted to the task or God) due to fault in character (i.e., that they should not focus on how the task will affect them, only on the competition of the task): serve God a person must be obedient and to be truly obedient a person must have humility. I read “take up his cross” to mean what I have just said, but to put emphasis on that it is not an easy path: to putout of a person’s own mind desires and focus on the wants of God. That focusing on “things of God” means the pursuit of eternal life (i.e., life in heaven) but only if a person commits his- or her- self to serving God for the purpose of serving God and not just to gain eternal life.