Sin is disobedience to God's will, not doing what we ought to do and doing what we ought not to do. Sin separates us from God and our brethren and it results in our loss of power, joy, peace and hope. It degrades us in every way and ends in our spiritual death. "The wages of sin is death" (Roman's 6:23).
We are asked to be perfect (St. Mt 5:48) and this perfection we find in the life of our Lord Yeshuva (Jesus). When we meditate on the perfect pattern that we find in the Life of our Lord (His love, humility, purity, prayer life, etc.) we find how sinful we are, and this makes us contrite, all the more humble, confess our sins with a contrite heart.
"If we confess our sins, He is faithful and just and will forgive us our sins and...