Can a temporary environment temporarily change your personality?

I was a totally different (and better) person in college than I am now. I feel more like my pre-college self now in terms of social anxiety, lack of self-confidence, having no motivation to do interesting things in my free time, and some other factors.

I thought I had grown and changed in college but now it feels like it was just a temporary environment that influenced me to be better for awhile, and now I’m just my same old shitty self.

Is this a thing that happens? Has anything similar happened to you? Is there something I could do to “tap into” my college mind even though I’ve lost access to my college environment?