1 Peter 4:1-2 says – Since therefore Christ suffered in
the flesh, arm yourselves with the same way of thinking, for whoever has
suffered in the flesh has ceased from sin, so as to live for the rest of
the time in the flesh no longer for human passions but for the will of God.
Here is what that means: As a Christian, you are to live your life for the will of God instead of human passions. In order to do that you have to stop the domination of sin in your life. To do that you must suffer in the flesh. And to do that requires a certain mindset, the same one that Jesus had.
Jesus was willing to do what it took to do the will of God. And that mindset leads to steadfastness in suffering. So, instead of turning to sin in your suffering, you turn to God, and thereby crucify your passions. It hurts, but it works. That’s what these verses are saying. Then instead of living for those passions, you live out the will of God.