Plan what you will drink before hand and stick to it. Don't rely on other people to supply non alcoholic drinks, they probably wont. Bring something really nice that you can share with others too. Bear in mind that these social events will get easier in time and it is natural that the first few times will be tough, so expect them to be, and don't see it as a sign that you need to drink to be social! And also, backing out is a totally valid option, as is leaving early x