Some people miss the ups so much that they're willing to tolerate the downs.
This... This is why I stayed so long. I kept trying to "get back to how we were" and that phrase came up many times in talks/arguments... The more that time went by, the fewer and fewer the good times became, and the worse the bad times got... .But I didn't change anything about who I was from the beginning of the relationship. So what changed?
If you find yourself missing the ups (and downs), it would serve you to look into why.
I think the answer to that is easy... The good times in these relationships are so good and so beyond what a normal relationship offers, that it literally becomes like an addictive fantasy that you want to keep reliving... That honeymoon and idealization phase is so good and such a rush, that who wouldn't want to feel that all the time?