Hello, my kitty is about seven months old, and he's always been very playful, and I love that about him, but recently his playful nips on my arm are turning into hard bites that leave marks. It's even gotten so bad that on occasions, when he's too playful, he bites my face. I need this to stop, but I don't want to discourage him to play with me. Any suggestions? This is my first cat, so I don't even know if this is normal. Please help!