I am an athiest. I have known many athiests and i have read many essays on the subject by athiests.
Most athiests dont "believe" that there is no God, they usually don't "believe" anything. Thats what is special about their system: its all falsifiable. The difference between an agnostic is that an agnostic has a truly reasonable chance that God exists. Athiests do not.
For example, i think that there is a possiblity that the God envisioned by Christians exists. I think that possibility is EQUALLY LIKELY as the possibility that the moive "The Matrix" happens to the be the literal truth of reality.
The possibility is so remote that it doesnt concern us. To quote Isaac Asimov, the president of the Athiest Humanist group at one time,
"I dont have the evidence required to disprove God, but i'm so convinced he doesn't exist that i dont want to waste my time."
That describes most of us perfectly. Its alll about the evidence, not a "belief" that there isn't a God.
And athiest means "one without the gods" or "one who does not belief in the gods" . VERY different than "One who believes that there is no gods."