How can I stop living for just him?

There is this guy friend I’ve considered a friend for a while – more than 4 years now. He’s been there for me through a lot and he is a great friend. However, I feel like I rely on him way too much. Whenever I am sad, sometimes I can only seem to be cheered up by memories of things he’s said to or done for me. It’s like I live for this one guy when I have other friends who care about me and I have family members who care about me also. Is there a way to destroy this unhealthy attachment without stopping talking to him?