Yeah, I was bullied as a kid, for pretty much the whole of my S2 year.
I found the move up to high school really difficult, found it hard to process the change moving from being in the biggest/oldest year at primary to being the youngest/smallest in secondary, for some reason.
Then, in S2, 3 of who had been my closest pals for years (lived near each other, hung out together all the time, etc) decided for reasons that only make sense to schoolkids to make my life a misery. And I made it worse by, rather than standing up for myself, going completely into my shell, and just sucking it up. And at the time, it felt like the entire S2 year piled on and joined in, though, looking back later, some other kids joined in occasionally, most didn't give a f**k, but for me at the time, it felt the way it felt. I didn't even get respite in the school holidays, there were threatening/silent phone calls to my house, things thrown at our windows, stuff like that. There was one guy who I knew thru the BB and the played golf with, who without being a nutter, could be a hardnut and knew how to look after himself, and he kinda railed against what was happening to me, and hung out with me, went out of his way to walk me to and from school, and such. If it hadn't been for him, I dread to think what sort of place I would have ended up in mentally.
It all kinda stopped in the summer between S2 and S3, though I never fully trusted those 3 in the way that I had done before.
My self confidence never recovered from it, and has always been a fragile thing ever since then. I have grown up thru my teens hating my reflection, looking for both physical and mental things about myself that I deemed 'my fault' and the reason people would want to bully me for. And to this day, in my mid 50s, I still occasionally myself looking in the mirror and doing myself down, especially now that I can add 'old' and 'bald' to the list of things to dislike about myself.
It's held me back in pretty much every job I've had, whether a new job or promotions, even though interviewers have spent time assessing me and deciding "yeah, he's the one for the job", I still get into the role and find myself thinking "I can't do this job, why did I put myself up for it" fairly frequently, and basically stressing myself out.
I've become very adept over the years at being very careful how much of myself I let friends and colleagues know about me - most folk I'd say would say they know me pretty well, but they don't, they know the me that I've allowed them to know. I've taught myself to have a personality that doesn't come across as "there's something he's holding back and not telling us", so people think they know me. There are probably only 3 or 4 people who actually know me completely, who I trust to be able to share how I'm really feeling with, without worrying that they're going to twist that knowledge back on me.
TL;DR bullying is shite.