A distinction between being happy and causing happiness needs to be drawn. It's easily imaginable for someone to find themselves waiting in vain for their unhappiness with no clue as to why the misery that they expected failed to show up. Happiness is more than numbness, comfortable or otherwise. It's not in the middle.
It was either Nietzsche or Schopenhauer who defined it as a preponderance of feelings of pleasure over feelings of displeasure. If you feel good more often than you feel bad, you're much more likely than not to find yourself thinking of yourself as happy. Does this mean a boundless appetite for pleasure is a prerequisite for pleasure? Or is it the appetite for pleasure itself? Contra Buddhism with more Desire comes greater happiness until even "life is suffering" itself becomes a goad and blessing?
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That was all terribly abstract. I can only speak to my own case: a multiple depressive episodes, some severe and debilitating. PTSD, traumas of one sort or another. An impoverished childhood. Oh, and ADD thrown in for good measure. I remember being surprised the first time someone described my life as tortured. That's certainly not how I think of my life, well at least not unironically.
There were times when I thought this last depressive episode was going to do me in. But afterwards? At times I was surprised to catch myself pleased with how I had handled myself there in the dark where even God doesn't see. That is what births confidence. The ego shattered, Dionysus torn to pieces. The self & ego are invented retrospectively.
I live for those times when I look my life over and find myself satisfied, sometimes even pleased, with it. The flip-side to this is that there are times when I am just as painfully dissatisfied and at odds with myself and my surroundings. It would seem the root of it all is feeling myself being the one deciding the good and the bad of my existence. To put it in a phrase: being the author of my actions and of my life generally.