I have a really hard time understanding my feelings. With a couple of romantic partners, I feel myself becoming happier when I’m with them. When they walk into the room, I get a little burst of oxytocin.

I don’t think I understood what it was in all instances.

Weirdly, I didn’t always feel at ease with them.

Like others have said: it varies from person to person. I haven’t felt the prosaic emotions other commenters described.

And, of course, it changes with time.