I would say the best thing you can do is keep a positive attitude through it and listen to your partners words as well as body language.

Ive had shifts where it was non stop and I asked over and over to get moved from drive. Cs, warming, hell just dishes would have been something but I was overstimulated (I have spd) and extremely overwhelmed. This was due to a really long line and just terrible customers one after the other. It was causing me to be short with not only partners but customers. Usually this isnt a problem because I can say "hey Im at my limit can I have help or be moved".

My words were ignored and when I finally spoke loud enough it was "well theres nothing I can do to help with that" even though I was offering solutions.

I would also say that your coworkers need to hop off the "you sound like the sm" your response can and should be "why is that such a bad thing? Im trying to be positive and theres nothing wrong with that." Dont let them shut your positivity down because someone else ruined it for them.

Good luck.

Closers tend to be pretty blackpilled, we get shafted a lot because we always have to clean up the messes of all sorts that happen during the day. We also suffer the most from thin staffing. I'm not surprised that they aren't really into your chipper BS, especially if it reads as disingenuous. Rather than trying to disrupt the mood, negative or otherwise, you might need to work on learning to read a room. Sometimes being negative is cathartic, a little gripe and grouse. NGL I hate the Cult of Positivity, I don't find it to be a helpful approach at all and people who behave like that certainly annoy the shit out of me so I can relate to the ones that are just not into you. Maybe you should try being for them by acting rather than talking, that tends to be more what closer types appreciate.