^ How fascinating! It's interesting to read of others' experiences.
Since other types are welcome.. I thought I would share that now I'm to a point where when I'm really happy/high/joyful, I revel in that.. I love it. I eat it up for all it's worth -- You could say I almost bask in it - simply because I know it will be short-lived in the grand scheme. So a detached part of me is definitely aware that it will not last, although for me it's never a background feeling of Hurt/sadness as is being describe. Rather, historically, it was almost a panic that once it receded I would be filled with the neutral or negative, which would feel far worse having just experienced the opposite. It was a premature bracing for the inevitable descent, as highs cannot be maintained in that sense.
So several years ago this was something I had a hard time dealing with, and it was one of the root causes of deep Anxiety for a while- my having a hard time coping with the changing, ephemeral nature of my emotions. My having to deal with them at all, as they never were really a focal point, in and of themselves, prior to my mid 20's. My getting to a point where I was unable to make heads or tails of the present, emotionally, because I was already in a state of dreading future unhappiness/negative emotions. Feeling prematurely consumed by future pain that I knew would happen, as that's life. Although through all of that I realized the fact that this stuff is so fluid also means that pain will never last either.. that I can turn it around and look forward to future awesomeness just as well. All of it just flows, and now the negative doesn't have any disproportionate 'power' any longer, thus ironically has lessened overall.
So for me I lean towards issues regarding future pain/future possibilities... the past doesn't really have a hold on me, at least once I've processed whatever ocurred in the past so as to be able to look forward. It's always a bit of an unsteady balance between the present and future, and often not knowing how to reconcile the two or which should hold more sway in a given moment.
And by this point, I've gone totally off topic.