Why is it good to be an optimist and bad to be a pessimist? An incurable optimist, as has been observed, really is just insecure about his pessimism. A pessimist, on the other hand, might be said to be a true optimist, since she at least doesn’t cower from the truth, and, accepting it as it is, endeavours to go on strongly despite it. These, no doubt, are sweeping statements, but the point that underlies them is that it is very difficult to tell objectively just how optimistic or pessimistic someone truly is; we have to take them at their word—but the very definitions of the words are so slippery that any self-professing of one’s stance is prone more to self-sophistry than anything approaching truth. To give an example: what makes a suicidal person pessimistic? Are they not in fact optimistic, given that they think suicide is a solution—that is, they actually seek a solution? Surely, if we define the optimist as someone who strives for and expects the best, then the suicidal person must be the most irrational optimist of all. More pessimistic is the one who considers suicide, but decides that it is worthless.
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.