Yes, I fluctuate too. It happens from transferences a lot, but also in therapy when I get really regressed (which has not been in a while).

I think it's really positive, most of the time. If it represents the free-spirited, spontaneous, carefree, innocent part of yourself. That's how it often feels for me. Although feeling like a teenager is quite different.

Up until i got really depressed, people often though I was half my age because I'd get spontaneous moments of this. It was fun and enjoyable. I think those parts of me have gone into hiding or something.