Is it like the frogs in the water, not knowing they're boiling until it's too late? Are we holding out for hope that will never come? Are we so damaged from our own upbringing that we think our dysfunction is normal? Do we think we don't deserve better?
All of the above.
I loved him so very much, but also for me, it was (false) security - I had become a stay at home mom very early in our relationship (for his daughter, and then for our 3 sons), so he was the sole breadwinner. After we moved to FL, he had a really good job with a promising future (he was being groomed to be the owner of a multi-million dollar company), so for me the unhappiness was kind of a trade-off for security. I had NO idea that things would get so bad that he'd quit his job and throw away his future. I NEVER thought he'd cheat on me and abandon us. But he did.
And once we get out of it, how do we learn to live healthy and whole within ourselves? How do we learn to not choose the same type of person if we choose to be with someone else?
LOTS of internal work. I have an amazing therapist who I've been seeing weekly for over 3 years now. The first two years of therapy were mostly him helping me survive the various crises that were happening. Now that AH has been gone for a year, and I've come out of that final massive crisis mode of everything hitting the fan, him leaving, and the aftermath of all that, the real work on my healing from a literal lifetime of dysfunction has begun.