I would differentiate the two. If you are not happy, it is not necessarily the case that you are feeling sorry for yourself. When you take emotional risks, and lose, there are consequences. Maybe the great can handle such things quickly and efficiently, but I think most normal people–everyone I know–has to go through a period of mourning/suffering, and it is not always possible to fully recover from a trust that has been deeply betrayed.
Just as some physical wounds leave scars that never fully disappear–and some that never fully stop hurting–so too does emotional trauma leave a mark. The mark is left in the patterns of emotional life: how trusting you are, how open, how enthusiastic, how willing to take risks. You have new decisions to make, and you change from one set of default assumptions to another.
Within my own world view, this does not become a sin until you start to become angry at other people for your condition. At that point, however, pain becomes self pity, and self pity is the foundation of resentment, which leads to chronic anger, hate, isolation, then aggression, and following rationalization.
We live in a culture of resentment, and that is why we see large skulls on large swathes of our popular culture, from t-shirts, to boots, to hats, to book covers. It is part of the reason why the horror section is so full in your local Blockbuster.
America has always been a nation whose people were inventing and reinventing their common culture, in response to constant change. Yet, historically we had at least a common appeal to Christianity, which itself–in direct and unmistakeable contradistinction to the can(n)ons of Socialism–gave voice to sentiments such as forgiveness, love and faith, and which countered the natural human urge to resent others. This appeal has been under attack for some time, and the doctrine with which we are supposed to replace it is one of constant anger.
You cannot build a nation worth living in from that basis.