I used to take meds (Zoloft® and Dexedrine® (dextroamphetamine sulfate)) to help with ADD and the resulting depression, but I stopped about five years ago when I started archery, which gets me thinking about the spot on the target and gets me into the fresh air. Focusing on the target helps to clear the mind and also teaches you to focus on other things in your life.
Yoga is fantastic as well. You can go to a class (my favorite), or pull out your mat and do it in your living room. If you are lacking motivation, go to a class; a good teacher will inspire you to advance in your practice. Yoga gets you to focus on your breath and body, and gets some nice chemicals running through your brain. I can go to a class with a migraine after a long day at work and come out feeling like a million bucks. When I found out my wife was cheating, I went to a class and felt so much better after. I do yoga at least twice a week, and I feel great and have a very positive outlook.
Also, volunteering to help others is a good way to feel better with a sense of purpose. One of the easiest is to donate blood. Sure, that’s only good every 8 weeks, but you can also donate platelets and/or plasma more often, up to twice a week. I get a rush every time I donate just knowing that I could be saving someone’s life down the road.