We are strong when we don't give in to our weaknesses and that is a spiritual struggle.: Keep watch and pray, so that you will not give in to temptation. For the spirit is willing, but the body is weak.
Christ praying at Gethsemane "And there appeared an angel unto him from heaven, strengthening him. And being in an agony he prayed more earnestly: and his sweat was as it were great drops of blood falling down to the ground.