As a negative one, I remember back when I was 10-12 years old in middle school I really liked playing videogames. I don't know how it was in the US back then, but here it was not as mainstream as it is right now. I mean, it wasn't weird, but most kids weren't as into games as I was. Anyway, I was talking with this friend of mine about how big of a change was going to be high school and she said "Yea, you are gonna have to change, videogames are just for little kids and you are beginning to be a bit of a freak". It really hurt and especially because the other kids looked down on me a little. Big hit to my confidence lol. Funny thing is that nowadays with the whole youtube thing and games being really big, the girl that called me a freak is now a big "gamer". She has 2 consoles, gaming PC and is always posting pictures of herself playing.
Positive one, quite recent actually. After my first year in college my Language teacher gave each student a personal talk about our performance during the year. I was a bit afraid because my grades were not that good and although he is a really nice guy, he is also demanding. He ended up congratulating me for my effort knowing that my grades did not actually reflected how good I was. Then he said "I imagine that you are teaching, aren't you? If not, you really should. You are prepared!". Before that, I hadn't really thought about working as a teacher just yet. Small comment that really boosted my confidence, after that I looked for a job and spent a really nice 2015 working 
Edit: after reading @cassiopeiic comment I remembered something else
During high school I was really shy. Not because I suffered bullying (luckily I didn't). It was just my personality. During my first year in college things hadn't really changed for me, but I had changed my attitude towards new people and I felt much more confident in that regard. One day, in a class, one of my teachers decided to do a quick play in order to explain something. He called me right away and I told him that I didn't want to do it because I was a bit shy. Some people started laughing as if I was making a joke. They thought it was a lie because I was always the cheerful guy in class. It felt good 
Edited by Scavi, 20 January 2016 - 02:13 PM.