Unintentional Sin?

I started Justification and Variegated Nomism, Volume 1: The Complexities of Second Temple Judaism. In this post, I will quote what Daniel Falk says about the definition of the righteous in the Psalms of Solomon (first century B.C.E.), on pages 46-47:

"It is not the absence of sinning that defines the righteous. The psalmist readily confesses that they sin, using some of the same terminology for the sinners. Nevertheless, the language applied to the righteous is only that of failure and lapse...They are never called 'sinners'...or accused of being unrighteous or lawless. Rather, their sins are unintentional and out of ignorance, and when they sin they willingly submit to God's discipline, atone for their sins, and are vigilant to root out sins from their household. They know and confess that God's judgments are just. The 'sinners' sin habitually...and do not recognize God's discipline but curse and sin all the more..."

I wonder what constitutes a sin that's unintentional and out of ignorance. I can see a person unwittingly violating a ritual taboo, but a moral law? I have a hard time calling a moral sin unintentional or out of ignorance (even if the Bible, Judaism, and Christianity considered certain unintentional sins to be in areas of morality). Even if a person is weak and part of him does not want to sin, there is still a part of him that does want to do the sin, otherwise he would not do it, right? This question is of interest to me because I have long heard Christians say, "What marks a true Christian is that he does not want to sin, and, when he does sin, he abhors his actions." Of really? Well, if he abhors sin and does not want to commit it, why does he do it?

Or there are Christians who respond to the argument of some gay Christians that "everyone sins" with "Yeah, but we do not approve of our sins, whereas gay Christians desire to continue their sinful lifestyle." But, if Christians do not truly want to sin, why do they sin? I'm not saying that I'm sinless, by any means. But I no longer try to prove to myself or anyone else that I am a "true Christian".