Today's Gospel reading came from Mark 8. Jesus began to teach his disciples that he must suffer greatly and be rejected by the elders, the chief priests, and the scribes, and be killed... Then Peter took him aside and began to rebuke him. At this he turned around and, looking at his disciples, rebuked Peter and said, "Get behind me, Satan. You are thinking not as God does, but as human beings do." So, how can we think as God does? The only way is to get to know him fully, and union with him provides the exact answer.
Later Jesus summoned the crowd with his disciples and said to them, "Whoever wishes to come after me must deny himself, take up his cross, and follow me." To deny oneself is one of the hardest thing to do, yet it is the way to freedom, to save one's own life. God cannot enter us if we are still in our way. Again, union with God provides the solution.