I think willful sin implies deliberate as well as knowing...? Someone can lose their temper, knowing that it is sin, nevertheless they forgot themselves for a moment and blew their top...it wasn't deliberate. There is grace for that if the person repents. It doesn't necessarily mean the whole tree is bad. If you have control over yourself and knowingly sin anyhow, that is another category...that is what I'd call willful, and if someone keeps on sinning that way they are in danger....no more sacrifice for that. And if losing temper and being nasty is a whole way of life for that person, without any care or remorse, then we might have reason to question the tree. Also there are sins committed without the person even being aware....we are usually the last to know our faults.
Whatsoever is not of faith is sin. Even the "good" that we do can be sin. Sin is more than just what we do or don't do, it is an overall condition or state that our flesh is in. As Paul wrote, " In me (that is in my flesh) dwells no good thing". Anything we do that proceeds from "self" (flesh) is sin really, even if it is not strictly "bad". Because it falls short and is not of faith, ie, spirit. We need the grace of our Lord every second of every day.
Yes sister, deliberate and knowing. But someone losing their temper knowing that it is sin is wilful sinning because he knows that he has to deny himself and carry his cross and not "murder."
Proverbs 30:14 KJV
There is a generation,
whose teeth are as swords, and their jaw teeth as knives, to devour the poor from off the earth, and the needy from among men.
Whoever does not deny himself and carry his cross and lose his life on earth cannot be Jesus' disciple.
Losing temper is not the fruit of the Holy Spirit but the work of the flesh (carnal).
Galatians 5:19-24 AMP
Now the
practices of the sinful nature are clearly evident: they are sexual immorality, impurity, sensuality (total irresponsibility, lack of self-control), [20] idolatry, sorcery, hostility,
strife, jealousy,
fits of anger, disputes, dissensions, factions [that promote heresies], [21] envy, drunkenness, riotous behavior,
and other things like these.
I warn you beforehand, just as I did previously, that those who practice such things will not inherit the kingdom of God.
[22] But the
fruit of the Spirit [the result of His presence within us] is love [unselfish concern for others], joy, [inner] peace,
patience [not the ability to wait, but how we act while waiting], kindness, goodness, faithfulness, [23]
gentleness, self-control. Against such things there is no law.
1 Corinthians 3:3 KJV
For
ye are yet carnal: for whereas there is among you envying, and
strife, and divisions, are ye not carnal, and walk as men?
Romans 8:6-8 KJV
For
to be carnally minded is death; but to be spiritually minded is life and peace. [7] Because
the carnal mind is enmity against God: for it is
not subject to the law of God, neither indeed can be. [8] So then they that are in the flesh cannot please God.
James 3:11,14-17 KJV
Doth a fountain send forth at the same place sweet water and bitter? [14] But if ye have
bitter envying and strife in your hearts, glory not, and lie not against the truth. [15]
This wisdom descendeth not from above, but is earthly, sensual, devilish. [16] For where envying and strife is, there is confusion and every evil work. [17] But the
wisdom that is from above is first pure, then peaceable,
gentle, and easy to be intreated, full of mercy and good fruits, without partiality, and without hypocrisy.
Losing temper over and over again at different times is someone who "keeps on sinning." Also, the Lord said to obey (not sin) is better than sacrifice (repent/being sorry)
1 Samuel 15:22 KJV
And Samuel said, Hath the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord ?
Behold, to obey is better than sacrifice, and to hearken than the fat of rams.
Whatsoever is not of faith is sin. Even the "good" that we do can be sin. Sin is more than just what we do or don't do, it is an overall condition or state that our flesh is in. As Paul wrote, " In me (that is in my flesh) dwells no good thing". Anything we do that proceeds from "self" (flesh) is sin really, even if it is not strictly "bad". Because it falls short and is not of faith, ie, spirit. We need the grace of our Lord every second of every day.
Paul wrote Romans 7 describing the time when he was carnal (in the flesh) (that also brings the fruit of losing temper, work of the flesh) He keeps on sinning although he doesn't want to. He was in bondage to sin. As you said, anything we do that proceeds from "self" (flesh) is sin even if it is not strictly "bad". But that means that we are not yet spiritual if the self (flesh) still lives. But Paul became Spiritual in Romans 8.
1 Peter 4:1 KJV
Forasmuch then as Christ hath suffered for us in the flesh, arm yourselves likewise with the same mind: for
he that hath suffered in the flesh hath ceased from sin;
Romans 8:1 KJV
There is therefore now no condemnation to them which are in Christ Jesus,
who walk not after the flesh, but after the Spirit.
One cannot both walk carnally and spiritually at the same time. To be carnally minded (flesh) is death. That's why we have to deny ourselves daily, die to self, including losing temper, so that the life of Christ would manifest. If we fail one time, then we are judged under the law and therefore bring us under the law.
James 2:10-11 KJV
For whosoever shall keep the whole law, and
yet offend in one point, he is guilty of all. (and those who walk in the Spirit has fulfilled the whole law by not causing anyone to stumble)
For he that said, Do not commit adultery, said also, Do not kill. Now if thou commit no adultery,
yet if thou kill, thou art become a transgressor of the law.
Only those who have ceased from sinning are exempted from the law. Like our justice system here on earth, if you don't murder, you cannot be judged as a murderer. But if you do murder, then you will pay the price under the law.
Whoever walks in the Spirit has already put to death the flesh. The flesh is dead, it cannot revive and commit sin again.
1 John 3:9 KJV
Whosoever is
born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
In short, whoever is born of the Spirit cannot lose temper anymore because that is not the fruit of the Spirit but the work of flesh. He has overcome sin and is more than a conqueror, the law has no power over it because with the law is the knowledge of sin.