I've said for a few years now my personality is slightly different when I speak English. I have a partner of several years that doesn't speak my language nor me hers and we communicate in English and even simple things like expressing affection feel different even after a decade.
At some point since I speak more English every day than my own language when I switched to "thinking in English" (not on purpose) I remember feeling very sad, having almost lost a part of me, and I spent some time trying to think what impact it was having on my own actions and behaviors.
Nothing major, but I am more assertive and outspoken in English than in my native language because things don't feel so "real" to say, so it's easier to not feel scared.
I feel very strange sharing this because when I tried I got strange looks but maybe someone recognizes themselves in this too.