You've been friends for a long time, and from your post, you've tried to be a good friend-- helping him out when he was depressed... lifting him up, etc.
However, friendships change. Apparently, your friend is now feeling well enough on his own and he wishes to spend more time with his girlfriend. That's his prerogative. It isn't that he values your friendship less, though he probably does take it for granted.
No need to be angry, but it's time to let go. You should focus more on yourself now. It's time to move on and make new friends.