My cat was kind of aggressive when I got him. I had to train him to be a gentle boy. If he was aggressive when he's on my lap or bed, I stop petting or playing and pick him up and place it him on the floor. If he was really bad, I put him in the bedroom where his litter box is and closed the door, and let him have a "time out". By being consistant, he did it less and rarely is aggressive anymore.