SIN is not believing the words of the Bible are true, also called unbelief. And sins are what mankind does because we do not believe the Bibles. 1 Corinthians 5:11 But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one no not to eat. Mark 10:19 Thou knowest the commandments, Do not commit adultery, Do not kill, Do not steal, Do not bear false witness, Defraud not, Honour thy father and mother. Romans 13:9 For this, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not bear false witness, Thou shalt not covet; and if there be any other commandment, it is briefly comprehended in this saying, namely, Thou shalt love thy neighbour as thyself.Galatians 5:19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.. . This is by no means a complete list but all of these are sins, but all a Christian has to do is ask for forgiveness, believe you are forgiven and realize this was why Jesus Christ had to die, for your unbelief in God's word. Realizing you are a sinner by nature, you do not become discouraged by your failing.