Beating yourself up is a waste of energy – the situation is what it is. You should be congratulated for questioning your right path in life.
As for the work situation, why would anyone have to leave in the first place? A change of mindset is required here. You're two people where the situation has changed and that's it. You're not his mother. You're a human being the same as he is and deserve the same right to happiness as he. Check you have the right emotions at work here – this is a time to rejoice you've made conscious decisions to fine your right guy. It's not a time for sadness, pity or sympathy.
Whatever guilt trip or negative emotions he's likely to project in your direction are his misguided emotions. Did you get that, they're his and not yours.
Man up, girl – go get that right guy who's waiting for you right now and live with happiness.