Well, it's normal that you are having a hard time with this as no one likes to feel powerless about a major life change. And when it happens unexpectedly as you described it can feel like a major rejection and it hurts. You most likely have moments when you feel anger and a sense of abandonment and lots of things can run through someone's mind in this kind of situation. So, it is a good idea that you find a therapist that you can sit and vent to and find your way forward despite how you experience all these feelings you don't know what to do with.

That being said, this decision is all about him, his discontent about himself and his life and recognizing that his youth is gone and that sense of freedom when younger. Yet, men do go through their own menopause where their testasterone levels begin to decrease. Some men feel depressed and confused by this as if "something is missing" for them. It's typically not something they even know how to articulate either. However, they see their own youth in their teenage children, and they also see it where they work in the younger men around them who tend to have more drive and get more attention because they are young and upcoming and this feeling of being on his way out becomes real and scary. And he doesn't want to FEEL this way either. So, this tends to bring on that "flight" feeling and it's not about you really either, but something he feels an urge to do within himself. This wraps him up in what you are describing where he says he is 100 % sure he needs to be free. Yet, it's not about you, but himself trying to fight something he is losing. It's not just psychological, it's physiological as well.