Pain, Depression and Pleasure
The thought-configuations that lead to pleasure are always carry the same theme: they relate to permanence, progress, acquisition, and dominion and physically, feel releasing. All those ideas are similar; those ideas that keep up sustaining so evolution has passively designed them for us. (Thanks, evolution!) Thought-configurations that lead to pain and strife also are linked thematically, and come in 2 forms, loss-depression and stagnation-depression. Loss-depression is feeling defeated and depressed because you have lost something valuable that promises prosperity -- money, romance, health. Stagnation-depression is much more tricky. It's the feeling that something is wrong just when things are not moving forward. In the body, it feels like tension in the shoulders and middle back. Pain always triggers pleasure-seeking via "positive" thought-structuring. Since pain is tied with stagnation, pain is the default feeling one feels.
An example. I lose a job. I worry about my financial future, my reputation, my future job prospects, my pride, and so on. I play memories of how I lost the job. I also play memories of what I did wrong. I might speculate about how others will disapprove of me. Together, all these thoughts form a painful thought configuration and I begin to feel stress in my back and shoulders. I automatically begin searching for a solution. The solution is to conjure up a new set of thoughts. (A) I can restructure my memories: reflect on the situation and challenge my thoughts of failure and my fears of humiliation, and in so doing, revise my view of myself. That new, self-promoting thought-configuration creates pleasure -- the feeling of progress and industry and the alleviation of physical stress -- and replaces pain . I can even try to think certain thoughts and offer myself affirmations of my value. (B) I can also make physical changes to my environment, contacting recruiters, maybe writing a letter to HR, or going on a vacation. All these decisions change the thoughts I hold in my head about the situation and stimulate pleasurable feelings. Anxiety, depression, status-seeking, romance, and careers all work according to the same principles.
Mankind's Hopeful Game
The great illusion is that pleasure can be made permanent if we get enough of it. So people engage in all types of thought-structuring (and environment structuring) efforts to amass it. But because it's linked with progress and movement, there is rarely any rest. As soon as you start to adjust, you begin feeling antsy again as stagnation-depression sets in.
And this is how human behavior works. ;)