“Bitterness”

Though it is a natural human trait, bitterness can and should be worked through and overcome.

Now also when I am old and grey-headed, O God, forsake me not; until I have shewed thy strength unto this generation, and thy power to everyone that is to come. Thy righteousness also, O God, is very high, who hast done great things: O God, who is like unto thee! Thou, which hast shewed me great and sore troubles, shalt quicken me again, and shalt bring me up again from the depths of the earth.
Thou shalt increase my greatness, and comfort me on every side. Psalms 71:18-21