Sounds like your buddy has lost interest; or possibly he's lacking direction. Maybe you should be more pro-active with him, some folks just need someone with whom to be creative and to bounce around ideas.
When something is your passion in life it is all you want to do. Yeah, you have to make a living, but all the rest of your time is spent on your passion. The only times I'm depressed - aside from real tragedy - is when I'm not doing what I love to do. To avoid becoming depressed when I'm not working for clients (and after I have finished the business end of my business which I hate but is a necessary evil) I'm adding to my sound library, experimenting with audio plug-ins, creating music (which is what I did for many tears before I got into audio post), watching/listening to films & analyzing the audio, participating in forums, mentoring, reading tech & "creativity" articles and books and visiting with my peers.