Paul writes in Hebrews that it is a matter of attitude...
Heb 10:26 For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,
Heb 10:27 But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
Heb 10:28 He that despised Moses' law died without mercy under two or three witnesses:
Heb 10:29 Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
A deliberate, premeditated choice to live the way of sin versus the way of obedience to God. John shows us that stumbling, making mistakes, downright sinning even is forgiven when the overall attitude is one of wanting to obey...
1Jn 1:8 If we say that we have no sin, we deceive ourselves, and the truth is not in us.
1Jn 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
1Jn 1:10 If we say that we have not sinned, we make him a liar, and his word is not in us.
1Jn 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
1Jn 2:2 And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
Tie this in to...
1Jn 5:16 If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it.
1Jn 5:17 All unrighteousness is sin: and there is a sin not unto death.
And we understand that it is a matter of heart. Paul spoke of sinning when he desparately wanted to obey...
Rom 7:13 Was then that which is good made death unto me? God forbid. But sin, that it might appear sin, working death in me by that which is good; that sin by the commandment might become exceeding sinful.
Rom 7:14 For we know that the law is spiritual: but I am carnal, sold under sin.
Rom 7:15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I.
Rom 7:16 If then I do that which I would not, I consent unto the law that it is good.
Rom 7:17 Now then it is no more I that do it, but sin that dwelleth in me.
Rom 7:18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
Rom 7:19 For the good that I would I do not: but the evil which I would not, that I do.
Rom 7:20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
Rom 7:21 I find then a law, that, when I would do good, evil is present with me.
Rom 7:22 For I delight in the law of God after the inward man:
Rom 7:23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
Rom 7:24 O wretched man that I am! who shall deliver me from the body of this death?
Rom 7:25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
