But Peter said unto him, Although all shall be offended, yet [will] not I.
Note 3 at Mr 14:29: Just like Peter, we often are more confident of ourselves than God is. Many of us are devastated when we fail in some area that we thought we had long since grown past. We need to realize that as long as we are in these mortal bodies, we cannot fall asleep at our battle stations in the fight against the works of the flesh (Ga 5:19-21). If we do, our flesh is just as capable of sin as anyone else's.
If we fall, it should concern us but not surprise us. We should simply realize with Paul that "(in my flesh,) dwelleth no good thing" (Ro 7:18), get back into the spirit through confession and forgiveness, and go on with Jesus.