It's certainly not a nice thing to get "used to," because it can colour your whole perception of yourself, others, relationships, and ethics, and not often for the better.
When I emerged from middle school, I was paranoid, depressive, jumpy, defensive, and aggressive, and I had a very difficult time trusting others. Even today, I have strong visceral reactions to people, places, objects, and other triggers which remind me of that period of my life.
I think what made it more difficult for me was that the bullying was executed in a mostly underhanded, sneaky way, which made it harder to pin down--lots of rumors, side comments, giggling, double entendres, veiled insults, snarky pseudo-niceness, thefts of my medical supplies, etc., and I didn't always know who was involved, and to what degree.
At some level, I would've preferred if people had been more overt and direct, because then that war would've been easier to fight, in theory.
I was excessively afraid of calling out people who weren't involved, and excessively afraid of causing the rumors or the teasing to escalate by doing "the wrong thing," so I mostly kept my head down and pretended everything was kosher.
In retrospect, I should've walked up to the main male ringleader, and bopped him in the nose. If anything, it would've been cathartic.
I also should've told my parents or other adults what was going on sooner. At the time, I believed that most adults either a) didn't know what was going on, and would make things worse in their goofy, invasive, "adultish" attempts to 'help,' b) knew what was going on, and had chosen not to intervene, for whatever reason. So, I erroneously believed that I had to shoulder it all myself, and that this was for "the best."