Aye, I can relate to that one DaaaBulls. I don't get it any more but I used to. It was like every time I met anyone at all, I was meeting the queen and had to be on my best behaviour, which I already knew wouldn't be good enough. Horrible, horrible, horrible.
Could it be that you're placing too much importance on other people? Just remember that they're only people, and that they eat, shit and sleep just like you do, and (without doubt) have embarrassing stuff in their past, and keep secrets, and all of that. Nobody is better than you. Or worse. And you blend into that more than you may think. Keep that in your mind, see if you can internalise it.
To tell you a small story, I once bought a necklace (or something similar) from a clothes shop not far from where I now work. At the time I was still very jumpy around people, just like you described. The shopkeeper was well into his 30's, a bit portly and, although not unkind, seemed unconcerned and detatched. At ease, I suppose.
All I had was £20, which was far more than the necklace cost, so when I handed it over I said, "sorry I haven't got anything smaller! Ha ha!" and without missing a beat, or raising his eyebrows at me, or making anything 'big' of what I'd just said, replied, "sorry I haven't got anything smaller," as he handed me my change and necklace in a bag.
I walked away somehow richer for that and I've never been all that sure why. I think it reminded me that another person could be unfazed whether I felt tense or not, so I might as well just not be tense. That's easier said than done, but that shopkeeper's always come to me when I feel tense when meeting another person.