How can a Depression sufferer already on meds have more "up" days?

I have suffered with some form of Depression and Anxiety for most of my life. I was diagnosed and began trying different doctor-prescribed medications 11 years ago. For the past several years, I have been on Wellbutrin and Effexor and they seem to be the most beneficial I've tried so far. I have experienced much higher levels of joy and ability to function. The problem is, I still have a lot of mood swings and unpredictability in how I feel from day to day. There are days when I feel really good and hopeful that I can be the person I know I'm meant to be. Obviously, I'm going to ask psychiatrist this on my next visit, but I was wondering if anyone had any theories or experience on how to have more "feel-good" days? I obviously try to practice lifestyle modification to help myself feel better, but sometimes it only helps so much and some symptoms seem out of my control. It just seems strange that my medications would seemingly work so much better some days than others. Anyway, thanks for any suggestions.