I decided a long time ago that I was going to turn this into my life, and it's going to be a solid decade before I'm ready to call it quits.
I get tired of modeling sometimes, especially when I have a lot of projects small projects, or I'm working through on big project. The best way I've found to deal with is to constantly look at other people's artwork, but 3d and 2d, and draw inspiration from the drive to improve there skills. I've made it a habit to spend an hour a day on DA, polycount, cgchat, and cgtalk, and that really helps to buoy my energy. Even if I don't feel like modeling for a week, I still find it encouraging and I'm ready to hop back onto my next project after a short break.
My social life has suffered alot because of this, but when I'm modeling I feel like I have a purpose in life and that I'm actually making headway toward my goals. As bad as feeling lonely can be though, its a helluva alot better than feeling like I fail at life because I don't know what I really want to do