I'm going to ditch my friend at the club despite being his designated driver.
Why would you leave your friend hanging like that drunk?
I don't know why, I just feel like his life is ruining mine.
It's understandable to want to part ways with a friend that you feel is holding you back, but choose an opportune moment to do so. If you already agreed to be someone's designated driver, then it's your responsibility to ensure that they get home safely. If you ditch them at the club, then they may not get home safely and you'll feel guilty.
I just want to ditch him so why does it bring back my responsibility; he should have thought about it before partying all night. Also, I'll bring him home later, not big deal.
Just make sure you both get home safely. If drunk, always call a ride sharing service to be safe.