We humans tend towards extremes. And, generally speaking, life is well-lived with things in balance. So it is with tip #12. When trying to shake the sad state, I have found it best to avoid the extremes of isolation and over-activity.
Either of these can push me towards feelings of depression and either can certainly prolong those feelings. Seems to me, that we can use "over-activity" as sort of anesthesia. Keeping ourselves "too busy" means we don't have time to deal with difficult issues...or to feel pain. Althought that might seem like a good thing, it's not. Pain is not always bad. It's an indicator that there is a problem that needs our attention. If we go without feeling pain for too long, we never address the problem. And so things get worse. Just as physical pain can be helpful (ever touch a hot stove?), so can emotional pain. Always avoiding the pain can lead to bigger problems. Too much busy-ness is just not good. AT ALL.
Just as too much activity/time with others is an extreme that we don't want to live in all the time, the same is true for isolation. Now, don't hear what I'm not saying. I strongly support time alone, time away from the crowds and routine demands. Time to refresh and replenish. And repair. But we were made to need other people- and for them to need us - and when we find ourselves continuously pulling away from friends and family and responsiblities....and pulling inside ourselves, we need a red light to go on in our hearts. Signalling trouble.
Happiness comes with a balance of time alone, time with others, time giving, time receiving. Check out your "extreme-o-meter" and see if you are registering too far in one direction or the other.