This causes difficulty quitting smoking

This causes difficulty quitting smoking - Try to ask people who have successfully quit smoking, they would answer, that quitting smoking is a hard thing done. American Cancer Society, researchers from the U.S., said that about 70% of smokers who want to quit smoking, but only 40% survive alone. They are 40% done in earnest. So that's why the rest of his bus failed? Even very difficult to do so?