How should I behave around people?

I'm having trouble with my stress levels when around certain people. I have terrible social skills, but recently I've been getting better. However, I had a disaster of a night at a guy's house where I just felt really horrible, like I was doing everything wrong, I felt like all he could see was the bad stuff when he looked at me, my mood changed drastically and I just felt agitated. It was the second time I had hung out with him. The language barrier pisses me off, he's Italian, I'm living in Italy so I feel stupid for not having learnt the language properly, I've been here 7months. I have noticed a trend where I act the opposite of whatever vibes I'm getting front the person I'm with. If they are stressed, I'll be chill. This guy was chill to the point of being horizontal and I don't know how to behave with someone who is so content, no issues, no anxiety. I think I acted like a ****, I felt like it would be best if I just got outta there. So I scampered early morning. Told him I won't see him again as it's easier for me to be alone, less stress.

Do I thrive on discomfort, was it just cause it was the day before my period, is it because I can't believe anyone wants to hang out with me, I.e. No self esteem.

How the **** can i sort this **** out so that I might be able to have a healthy, stable relationship in the future.