My partner and I had several years of couples therapy together, and I can confirm your thesis in thread is spot on, great comments. You have to be able to grow together, live through the parts where that new relationship energy and passion are burning lower than they used to (and not act out destructively because of it, lots of ways to accomplish this, limited only by negotiated boundaries of the relationship), but still be able to check in with each other to ensure each other's needs are being met.

IMHO marriage is about finding a teammate, not a soul mate. It is more of a business partnership than about fairy tales and romance, and I think too many folks don't understand that upfront. TLDR: You are looking for a life cofounder; choose wisely.