So you got picked to be the designated driver. Looks like your evening is going to be alcohol free. This sucks. You will protest a bit, saying things like "Why do I always have to be the one to drive", and "Maybe we'll walk!" but it's no use. Tonight, you were chosen for duty. You might as well try and have a good time anyway.
I guess you don't really have to drink. There are plenty of perks to not being drunk at the party. You can stay sharp enough to be able to count how many pretzels you eat so to not ruin your diet, you can have a conversation for more than 10 minutes without having to go to the bathroom, and no matter what you say, you seem smarter than everyone else because your breath doesn't reek and you don't add 'woohoo' to every sentence. Yeah, this whole designated driver thing just might work.
Wait a minute, not drinking might actually be better! I mean, think of the power you're possessing here. You're the only person in here that's not completely drunk. You are surrounded by people with bad judgement and poor control over their body and actions. With your sobriety super powers, you can stand aside and watch everybody else make mistakes and behave in ways they will definitely regret tomorrow. And while no one else would remember what exactly happened -- you'll be the one with the answers. Use it to make fun of them, blackmail them, or simply remind them what they did and prevent another 'Hangover' movie from happening.
Who are we kidding, though? They had a blast in those 'Hangover' movies. You would love to join in the fun right about now, instead of being the one person who is sober enough to organize everyone's pizza orders. By this point you want a drink so bad you're even jealous of the idiot who broke his tooth doing a keg flip.
What if you just had one drink? You won't get drunk, just feel a little more like a part of the party. No one is watching, you can slip one bottle, they'll never know. Surely all your friends do it when they are the ones who are the designated drivers. Besides, you're not going to leave any time soon - by the time you go home the effects will wear off. There's a bottle right there, just staring at you. You know you want it...
Nah, you're not gonna do this. We all know you're responsible. That's why you were chosen to be the designated driver in the first place. You won't have a drop to drink tonight, and you should just accept it -- you are the driver. You were born to drive. You're like 'Fast and Furious' Vin Diesel combined with Ryan Gosling in 'Drive', with a bit of Angelina Jolie in 'Gone in 60 Seconds". And just a tad Will Ferrell in 'Talladega Nights'. Okay, I can't make it sound cool. You were screwed over tonight. You'll make up for it in the next party.
This is where you make all your friends hang around the back seat while you drive for hours looking for a taco place, because you control the car and they can't do anything about it.