A quick backstory to explain where I'm coming from:

I left my last job over 6 months ago, it was a pretty steep jump up in responsibilities from volunteering in the same sector, I was working with a very vulnerable client group. Basically I liked the client work but much of the time I was office based which is not at all me, add in we were a new service and my manager chopped and changed what she wanted frequently contradicting herself, switching between being supportive and blowing up in temper at me. I had one colleague who was on long term sick leave most of the time I was in the job and I covered for her, she was the more experienced of us two but I didn't receive any mentoring or guidance because she was not there much. It sounds like I'm making excuses, I do think there were failings on my part, but it was not a good environment for me and I ended up stressed to the eyeballs, worked my notice and went on SSRIs.

Where I am now:

I am doing well on the SSRIs, feeling well and have been applying for very low responsibility basic/minimum wage jobs, not getting interviews or anything promising until today. I got invited to a recruitment day at a supermarket following my application and online tests, so I've read up on how they do these and it seems quite informal, team games, aptitude tests. From what I read the main thing they are looking for are good communicators and a 'light touch', so it's a case of rubbing along well with everyone and being relaxed. It's a stock job so customer interaction will be important.

I'm going to try to be as relaxed as I can, I usually tense up in interview situations, although in my every day persona I'm a smiley kind of person (and get told so), I need that person to come through. I just tense up when I know I'm being assessed.

Any tips on these kind of events?

Any tips on keeping calm and confident?

Also, any thoughts on what I should say if asked about my previous job? So far I'm thinking about saying it was more office based than in the field and this did not suit me (both true) and not mentioning anything about the negative stuff regarding lack of support from my colleague and craziness from my manager.

Ty