The breastplate covers the heart. Damage to the heart could be more server than you know. Jesus, even though he knew in advance that Peter would deny Him, prayed for him. Not that Peter wouldn’t deny Him, but that Peter’s faith would not fail. Jesus came after Peter as quickly as He could after He was risen from the dead, reassuring him of His love. Now you put on the breastplate of faith and love. You haven’t done too much for God to cast you away.
Mark 16:7
But go your way, tell his disciples and Peter that he goeth before you into Galilee: there shall ye see him, as he said unto you
1 Thessalonians 5:8
But let us who are of the day be sober, putting on the breastplate of faith and love, and for a helmet, the hope of salvation