Umar RA said,

It is attributed to Umar ibn al khattab radhiAllah anhu that he said, 'Take account of your deeds before the account is taken from you'.

Another saying of Umar radhiAllah anhu that i like is, he said that best reply/retaliation to an injustice done to you and a disobedience to Allah subhanahu wa ta'ala's command regarding you is, you sticking with the laws of Allah subhanahu wa ta'ala and obeying Him to best of your capacity.