Quick story...
I remember the time a wise old "ladies man" taught me this lesson.
He said:
Relaxation is actually pretty easy in groups... because your muscles have a rather binary switch... they're either tensed (to some degree) or they're relaxed.
The question is: which muscles should you relax, and which not? I think you'll be able to figure this out for yourself. (Obviously, you want to keep your legs and spine held up straight) For some reason, I find it really beneficial to relax my shoulders and face in set.
But I find there's a deeper way to look at this topic, and this comes directly from being in-field for 100s (maybe 1000s) of hours every year.
Relaxation is not the same as comfort.
Naturals are COMFORTABLE with girls... but not always relaxed.
Being comfortable in set, to me, means three things:
1. Slowing down/shutting off ALL internal rep systems (the pictures and movies and sounds in your mind)
2. Having a good feeling spinning through your body when you're talking to women and
3. Having an OUTWARD focus, on the girl in front of you. (All while your muscles are relaxed and you're feeling good)
The point you begin to take control of your feelings (which I can tell you're looking to learn), is the point something inside clicks and you know your bed will be warm for the rest of your life.