The defining characteristic of pessimists is that they tend to believe that bad events will last a long time, will undermine everything they do, and are their own fault. The optimists, who are confronted with the same hard knocks of this world, think about misfortune in the opposite way. They tend to believe that defeat is just a temporary setback or a challenge, that its causes are just confined to this one case.
Learned Optimism: How to Change Your Mind and Your Life (ed. Vintage, 2011) - ISBN: 9780307803344