A Cynic, by definition "Of or related to the belief that human actions are motivated only or primarily by base desires or selfishness; skeptical of the integrity, sincerity, or motives of others; bitterly or jadedly distrustful or contemptuous; mocking; showing contempt for accepted moral standards by one's actions ..." Most cynics are not pessimistic or even generally negative, and in fact, I would consider myself a realist; and to that affect, believe that realism bares many more cynical children than pessimism ever could.
A cynic sees the world for what it is, neither the rose coloured glasses of optimism or pessimism are worn, and this hardens us to the various ways of the world.
I, as a cynic, would even reject parts of this definition, because I do not see selfishness as a bad thing (see Ayn Rands "Virtues of Selfishness"). I also believe that there is good in all people, but how much that is remains to be seen, and is usually covered up by normal human nature/emotions/motives.
I am a cynic, a realist, and laugh in the face of failure, and I wouldn't have it any other way.