I’m not in the position of giving real medical nor therapeutic advice, but just realized couple of things while finally getting out of the loop, which took me months of education and control.
There are numerous tries and failures and decisions I went through to finally set my brain conscious comfortable choices when I feel distressed or too excited (my habit triggers).
I first tried painting my nails with nail polish which was disgusting to smell/taste, but it didn’t do much to me, I kept doing it and the polish was going off (and spitting it out) each time I was nail-biting.
Other attempt to stop this was when I tried to draw markings with a pen around my nails and notice them whenever I felt like I was going to do anything. Didn’t do much either.
I got it settled when I tried to reach the source of the reasoning and the triggering of my habit, so I calm myself down, don’t get over excited and if I’m feeling stressed, I’m just trying to intentionally look out of my nails, as they’re important in that situation, so I know that even if I’d bite, I just don’t, rubbing on them and do the stuff I was doing. It’s self education, I say.