I definitely feel better when I'm with people who expressed genuine happiness and when I read things I truly find motivational. That said, I feel instantly better when I quickly complain about something and am understood. I'm not saying this is a good behavior to do all the time, but it's a quick way to blow off steam.
One thing I'd add about gratitude: the deeper I can go with it, the better. So, instead of listing the same old, tired things I'm grateful for, if I take one thing, say, the Internet or my friendship with So-And-So, and make it come alive, I feel much more grateful in the moment. Like, bringing up good memories, thinking of things I will do in the future related to the object of my gratitude, ETC.