I still feel wrung out after I've done half an hours aerobatics. So yes, this stuff wears you out even after a lot of exposure. But trust me, you do get used to it. It just requires a few flights to build up your tolerance.
And no, I don't think low/high blood pressure has a direct effect on nausea, unless the situation is so extreme that it causes all sorts of side-effects. But then you'd probably not fit enough to fly in the first place.
What does have the most effect is feeling well. Well fed (but not overfed), well rested, excited (but not apprehensive) about the upcoming flight, well clothed (not too warm) etc.