Matthew 16:24-25 - Then Jesus said to his disciples, "If anyone would come after me, he must deny himself and take up his cross and follow me. For whoever wants to save his life will lose it, but whoever losses his life for me will find it."
As you read through the whole chapter of Matthew 16, you will realize that before Jesus said this, Peter recognized Jesus is the Son of the Living God, he knows that He is Christ, the One whom God sent for mankind. Jesus said Peter knew it not by flesh, but by the revelation of God. However, the next thing is when Jesus started to reveal on His redemption plan to the disciples, again Peter took him aside and began to rebuke Jesus saying that "This shall not happen to you!"
You see, as a man live by natural perspectives, whatever he sees tend to be limited. He will not grasp the power and the plan of God, and it causes him unable to move in the power of God. Peter in a sense was trying to stop Jesus from fulfilling the plan of God, though his intention was to protect Jesus. Jesus then said whoever loves his life will lose it, but whoever loses his life for Jesus will find it. He doesn't mean to die, but He means if you esteem your own life more than the plan and the Word of God, you will lose the real life that you could enjoy! And many of times if we are to live in our own natural perspectives, we are bound by limit. And the will of God is that we to live in Him, and in Him there is limitless! That's why we lose the real life that Jesus wants us to live, we missed the full potential!
However, Jesus said but if we will esteem His Word more than our own selfishness in life, we will find life! The matter lies on how much we weigh His Word, just like Peter, a moment before that he esteemed Jesus as Christ, but the next moment he stopped Jesus from fulfilling the plan of God. Therefore, many of times, the devil will try all sorts of way to trigger us to live in flesh, selfishness, and in natural senses rather than living in the very Word of God. The natural tends to hinder us from moving into supernatural, however, we are to be like Jesus, rebuke all the things that are not in line with the Word of God, and start to esteem Him more than ourselves.
For it is not I who live, but Christ lives in me, Paul said (Galatians 2:20). So it is not we who live now, but Christ in us.