How do I convince my husband that his addiction to marijuana is going to destroy us?

I've threatened to leave, I've screamed, I've cried, I've ignored him, I've lavished him. He gets help and quits within a month. He tells me I'm just a "nag".

: http://alcoholdrugstreatment.info/how-do-i-convince-my-husband-that-his-addiction-to-marijuana-is-going-to-destroy-us