There are lots of ways to approach this. Tell them you are taking some time off from drinking. Or, tell them you can't take the hangovers. Or, you feel sick when drink, the negatives outweigh the positive. Or be completely honest and say you feel that you are having a problem and want to nip it in the bud. This is what I said to my friends and family: "My drinking days are over." Everyone was cool with it. People don't care as much as you think they do.