how do relationships happen, how do they work how come people can last soooo long ?

From what I can tell, the secret to a long relationship is to lower your expectations of the other person, and raise the expectations on yourself. A few decades ago, everyone knew their responsibilities, and it was unthinkable to put yourself ahead of society, even if that meant dealing with a shitty relationship.

Nowadays, me-first is the norm, and a relationship isn't worth keeping if you don't feel ecstatic at all times, see someone else you might like, or your partner doesn't fill the gaping hole of meaning built into the human existence.