After Jesus arrest and crucifixion Peter was a broken man. Peter was Emotionally Broken. Peter was Spiritually Broken. Peter was Mentally Broken.
Peter had promised Jesus at their celebration of the Passover meal and institution of the New Covenant Meal that he would never deny Jesus. That he would be the most faithful follower Jesus would ever have.
And then within a few hours Jesus is crucified violently.
And Peter was confronted with his frailty, his humanity, his unfaithfulness, his weakness. He realized he wasn't who he thought he was. Peter was broken.