It's understandable that St. Peter, and likley the other apostles, didn't want Jesus to suffer, which was seen as some kind of punishment from God. Yet when St. Peter rebukes Jesus, He makes clear that he thinks as humans do, not as God.
Then Jesus says the way for disciples following Him is to also experience suffering. As experience has shown over the centuries, we face suffering because the world opposes what we stand for in the Truth of God. Like Jeremiah the prophet, we might grow weary of following this way. Yet he acknowledges that when he aims to stop, the Truth becomes like a fire in him, and he can't hold it in.
St. Paul, in the 2nd reading, urges us to be living sacrifices, offering ourselves for God, which is how, in the midst of the challenges of being a disciple, we can find purpose and even joy, as we worship God from the heart. We turn our focus from world ways to focus on God and discern His will.
Ultimately, Christ will die, and then rise and enter glory. We have the chance to share in this glory, after we struggle and suffer, while living with wholehearted devotion to God and following His will, as a reward for faithfulness to God.