One should have strong courage and conviction. Think of your parents, think of loved one, think of children. You cannot go on smoking and drinking for nothing, but only to spoil your health. So a strong determination and disciplined living is required.
it takes a lot of discipline on the person to be able to quit..i think all you can do is to talk to him about the health risks of the vices he is in to..but it takes a personal decision to really quit it..