The only way I see, Is to help him be more positive about his own life.
Or,help him out with some of the major things holding HIM back.
Your friend, Is probably just scared you'll not want to be his friend anymore.
Especially If your doing THAT much better than him.
Kinda like when a girlfriend/boyfriend starts to get all clingy when they are scared of losing you.
Have you asked the person how they have been doing lately?That sort of thing??
IDK, thats just my take on it.