My son, do not forget my law, but let your heart keep my commands; for length of days and long life and peace they will add to you. (Proverbs 3:1-2)
We, unfortunately, have this innate tendency to forget that which is contrary to our sinful natures. We repeatedly need to be reinforced and reminded to do the things we know to do. Because of our propensity toward sin, being told once is not enough. This may be why there are four gospels and that the commandments of God are repeated time and again in the scriptures. For example, reading our Bibles once or even twice is not enough. We ought to be in the Word of God daily: reading, studying and memorizing it. Likewise, we get spiritual reinforcement from each other. We are to be in regular fellowship with other believers: studying, praying and worshipping together. This is one of the main purposes of the Church of Jesus Christ: that we would not forget God's law and that we would keep His commandments, so that we may have full, prosperous lives.