I have been through a couple of things I see as tiny rejections: - not sure if this is the right word to describe it - shameful situations that make us overthink for days?

- I was asked to help a group of people at college. They have this project in progress and needed suggestions on something specific I happen to be really interested in, even though I'm not a specialist. I was feeling confident to be helpful as one of the teachers involved is nice with me and researches on subjects I'm interested in. When I entered the room she introduced me to everyone, including the other (head-of-the-project) teacher... who didn't recongnize me. She had seen me before other times, we have sit together in an occasion or two (but I don't think I talked very much as she's too outspoken and makes me uncomfortable), still she let out a "oh, you're not from here, are you?". Now I know people who deal with lots of students might forget faces, but I'm far from being a freshman... anyway, that disturbed me for the rest of the presentation (that went well, I must add). I just kept listening to this voice telling me I have no presence, I'm blank and easily forgettable.

- Another teacher is looking for an intern and called two of my colleagues asking if they wanted to join. He always see us together in group works, but I didn't get a call. I e-mailed him about another subject days before and he replied after my acquaintances had received the calls, but never mentioned the internship. I'm wondering if I'm not that good, if I don't stand out (and the requirements for this internship aren basic. Technically, I'm sure I qualify...).
Maybe he didn't say anything because one of my acquaintances asked me, right after they got the call, if I was interested because they would have to decline due to their busy schedule. So he probably mentioned my name and then told I wasn't avaliable (I declined due to my schedule too). I don't know, I really respect this teacher and not being considered for the job even when we have some contact made me feel stupid. I must have done/said something stupid during classes, or maybe I'm not as good as my peers?

I'm overthinking about this for over a week. Damn.