D.L.
My inspiration = "and this too shall pass"
I have 3 boys, 18, 15 and 12. My 18 yr old is now polite and friendly, he started the grumpy behavior at 12 and it got worse thru about 16 1/2 - then he started slowly becoming human again. Now I LOVE spending time with him.
As for my 15 yr old - OHH he is a challenge every day.... If he smarts off to me, or is dis-respectful in anyway - he goes no where that day, or the next day. He gets really mad, then he'll apologize and it will be a week or two before it happens again. It's just all part of growing up and it will get better. Just be firm and be consistent..
Good LUCK
D.