The no ball is the bane of the fast bowler. Just ask Sreesanth, who is infamous for overstepping.
You charge in, trying to exert every last ounce of pace onto the ball, finally get the edge you want into the keeper's gloves.
And the umpire calls the dread two words; "no ball!"
The worst part of it is that although you only have yourself to blame, you have no idea how it happened.
It's a terrible habit, but like all habits it can be broken.