I wish I had been able to apply such a philosophy sooner in my situation, but the reason I didn't, and couldn't, is one that is ignored by this philosophy. My kids. My young kids who were being put through h*ll by their mother's reckless actions. I couldn't just say "Fine. You want him, you can have him", because I would effectively be saying "Fine. I freely give up half my kids' lives, and have no problem with you bringing a predator step-father into their lives." I was also grieving horribly for the loss of the family the kids were enduring. When kids are involved, especially young kids, it's not a simple act of letting the wayward spouse go, because they take some of the kids' lives with them. No court in my state would have ever awarded me with full custody.
Nobody here has ever advocated that thinking. Your WAS is already splitting time with the kids and introducing the OP to them. That's why you have a L, Gucci calls it "having your ducks in a row." Seperation/Divorce agreements have some very specific language about time your children can spend with other adults. Break a judges order and see how that works for you.
A WAS and their L know how to prey on your "feelings." A good DBer will check their emotions/feelings at the door (detach), use their brain and combat their WAS feelings with feelings. You can't apply your logic to someone else's feelings and expect it to influence them. You change how they feel about you.
"What is best for my kids is best for me"
Persevere = happily being patient over a long period of time