It's hard because from the sounds of the way he is trying to launch back into life, he is probably internally beating himself up pretty hard over the fact that he keeps finding himself missing her. I used to be pretty angry with myself, especially since I had so many real reasons to hate him yet mourned the passing of our relationship, it merely added to my view of myself as weak and broken in some way.
My friend, who had been through something similar herself was great at making me stop hating myself for this weakness. I could call her anytime, day or night, home or at work and she would help me through it. She never made me feel like I was weak for hurting, and she never made me feel like I had to be here, in the now, coping with my loss.