I think one of the main reason most people have such a hard time is bc vape shops always suggest such low nic content for starting out... Myself and my gf needed 18 and that seems to be a good number from what I've seen. A lot of the freinds that I know who have quit have struggled with it at first, all of them were given 3-6mg
juice though... a few of them who asked, I just mixed them some high nic
juice and it made it a lot easier.
My coworker was using some 6mg juice for his third time trying to quit, but said it was doing absolutely nothing for him, I just increased it to 16 for him last week and he said he could tell the difference almost right away.