First of all, not all sins are willful. As much as I, or anyone, tries to avoid sin, we are occasionally going to trip up or be put into a difficult position. Look at Rahab, an ancestor of Jesus Christ. Rahab was put in the tough spot of telling a lie to save the lives of Joshua's two spies. Would it have better for her to avoid sin the sin of lying by telling the truth about the spies she had hidden in her home?
Second, even knowing that it's not possible to lead a perfectly sinless life like Christ did, I believe you should try your best not to sin. And I think assurance theology is dangerous. I think some people use assurance of salvation as a rationalization for willful sin. I also suspect that people who purportedly repent but then go on leading lives of sin probably did not repent in the first place. But if they did truly repent, but then go on sinning, I would encourage them to read about the consequences:
If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, (Hebrews 10:26)
I believe what I read in the bible. And this verse seems fairly straightforward. /jmho
=====================================
As much as I love conversing with you about bible topics, I don't get paid when I goof around on the Internet. I've got to get to work. Godspeed to you in your Christian endeavors!