Yes, I agree that it gets easier with practice too.
I for one, would not have been angry with one of my friends who wanted to go alone to the beach. That's just strange reaction to me and an unhealthy one too. Rather immature and selfish really when I think about someone doing that to me. Plus, if I had a problem with something someone did or felt left out, I would calmly and gently bring up what was bothering me in person, but that's just me. I still don't see what the problem is really. So you needed to be alone, doesn't everyone once in a while?