Heathcliff was abused by his brother from the moment he was brought to Wuthering Heights. This embittered him and made him lash out at many people. In addition, him and Catherine remained in love with each other, however, Heathcliff was devestated upon hearing Catherine state that it would be beneath heer to marry Heathcliff. Heathcliff ran away and didn't return until after Catherine married Edgar Linton.

I'm not sure that it would be accurate to say that Heathcliff's actions are motivated purely by revenge. Instead I think his actions after Catherine's death (his abuse and cruel exploitation of Hindley, Isabella, Hareton, the second Catherine, and Linton, his own son), are the product of his loss and confusion. The loss of Catherine is akin to Heathcliff losing half of himself. He is trying to hurt those he thinks responsible for his loss, but at the same time he is a walking contradiction. Others around him don't understand his motives and feel he is driven, at times, more by madness than by revenge.

As for what stopped him, Heathcliff himself stated that the act of destroying others stopped making him feel good. It lost its joy. Toward the end of the novel Heathcliff confesses to Nelly that he no longer cares for revenge: "I have lost the faculty of enjoying their destruction."