All this implies that the suicidal person gives a certain amount of reasonably logical thought to their decision. This is not always true, but if the act itself occurs in a moment of utter despair, or pure irrationality, then surely we can have neither optimism nor pessimism. In that case, even though we can say that the action itself is not one or the other, the person overall is more likely to be an optimist, since an optimist is more likely to be an idealist, and an idealist is less likely to be able to handle eventualities turning out far from ideal.

On another note, it has occurred to me that if to be an optimist is to believe that this is the best of all possible worlds, then a theist, assuming that he believes in heaven and that heaven is a possible world, must be a pessimist, despite his apparent optimism about going to heaven.