Willful sin is where you know that it is a sin and you tell yourself I know it is a sin but I am gonna do it anyway. It's especially hard when she is standin right in front of ya naked as a jaybird.
That is pretty much believer definition. What makes it willful is awareness. So, willful means that you were taught it was a sin but you did it anyway.
According to the defintion, a person chooses to sin, not matter how he rationalizes or justifies his sin, and that is why it is willful.
No justification, according to the definition.
Although, concious sins involving conduct are made by choice, human weakness at the time is a defense. Ajudicating the difference involves determining whether the sin involves mometary weakness. If a person repeats a sin, that could be an indication that the sin was made by choice. Because the next time around, he should have been well prepared.
Are all sins willful? I do not believe they are. Everyone sins a lot without even without being aware of it, for example what we say and do or fail to say and do, our thoughts our feelings, desires, eq: ( "You must not desire...." compare".. "keeps on"...)
The key difference is mometarry weakness that is not repeated or wilfull choice.
But lets cut to the chase here: Accountability according to the Bible. Will God buy your defense? Although Christianity teaches the ransom, it also teaches punishment after the ransom. If that is the case, will God accept your reasons? If there is no God of the Bible, then you have nothing to worry about.