Each of us (chooses) our own friends, lovers, and spouse.
We get to decide whom we give our phone number, email address, and how much time we want to spend with someone. We say "yes" to dates, to kisses goodnight, to additional dates, to sex, and marriage.
An absolute "no" would have stopped things in their tracks and there never would have been an opportunity to fall in love.
Essentially if we get to choose who we spend our time with then we're controlling who we fall in love with.
"how else do marriages last 20 plus years without the commitment to one another that you are going to out effort into that relationship and make it last?"
Several years ago a young radio host asked her 85 year old grand-mother; "What is your secret for having a 60 year marriage?"
The old woman replied: "Baby, we just stayed together."
If two people decide that no matter what they say or do to each other (divorce is not an option) then having a lasting marriage is fairly easy.
I know married couples who live in the same house but in different quarters. I also know of married couples who live in separate houses but get together for family and company events. There are other married couples who cheat on each other discretely or tolerate some form of abuse and they have no plans to leave.
In our society we tend to measure the success of a marriage by how long the couple remains married and not if they're still romantically "in love". There are lots of "emotionally divorced" married couples!
If neither person has any "deal breakers" or "expectations" then simply (staying together) is a piece of cake!
There are only two ways to experience joy and peace of mind in relationships: We either get what we want or we learn to be happy with what we have. Accept them as (is) or move on.
The choice is up to us!