So you made a mistake or two in your roarin' 20s. Don't worry, that's all part and parcel of that decade in your life. In fact, you should actually be thankful you made these blunders, so you'll arrive at your 30s with experience that will prevent these mistakes from happening again.
Source: Warner Bros. 
The Work Mistake That Made You Sweat Buckets
If you're here reading this, the world has probably not ended because of a mistake you made at work. Sure, in that moment it was probably the worst thing ever, but you've learned a really valuable lesson from the experience. In fact, it's a good thing that you're making the mistakes early on in your career. These snafus can still be chalked up to not having enough experience.
The Impulse Buy That Led to Eating Instant Ramen For a Month
OK, so you just had to have that pair of Louboutins! After caving to the temptation and buying that wallet-draining purchase, you'll hopefully realize that paying rent and eating are more important.
If eating instant ramen for a month doesn't drive the point home, perhaps you'll finally realize the fallacy of it when the item is no longer trendy. Or maybe you won't, but that's OK, too. We all have our weaknesses and our 20s are the time to embrace them.
Source: Meme Crunch 
The Drunk Fiasco (Fiascos)
Hey, you need to know how much alcohol your body can tolerate before you reach a point where your friends can't tolerate you. These drunken mistakes may even help you realize you don't need alcohol to have fun. And you'll probably arrive at the conclusion that the world's worst hangover is never worth it.
Playing Things by Ear
Now that you've grown up a little, you've realized that playing things by ear isn't always the smartest strategy. But while you're young and enjoying life, you don't have to be bogged down too much by the restraints of structure, practicality, and common sense. It's nice to throw all caution to the wind sometimes. And it'll get harder to do so once you put on your grown-up shoes and start a family.
Source: Bravo 
Toxic Relationships That Deserve Their Own Show on Bravo
Be it a toxic friendship or romance — trust me, you've learned a lot from this pain.
Maybe you felt pity for your pal or even special when she chose to "bless" you with her attention. Whatever the reason, this lethal encounter will help you figure out who your real friends are. You'll also hone your cray radar and learn how to stand up for yourself.
You might be smacking yourself with how dumb you were for falling for that jerk, but that experience is going to make you really appreciate the prince (or princess) charming that will eventually make an appearance in your life. And you'll be the Yoda to your friends who will navigate the perilous waters of douchebaggery.
Source: Bravo 
YOLO may be a legitimate excuse for all the cringe-worthy mistakes you made while you're in your 20s, but you won't be able to rely on it in your 30s, so it's a good thing you wore it out before you put it to rest!
It'll be great fun to relive those crazy YOLO moments with your friends when you've graduated into the grown-up world. You'll never need to wonder what you're missing, because you've lived it and wouldn't choose to live it over again.
Not Getting Enough Sleep
Your 20s can definitely be a very sleepless time. Between staying up with your friends to close a party to pulling an all-nighter for an exam, you'll wonder how you even functioned.
However, you may experience some of the best and most memorable moments in those times — the all-night study marathon with your best bud or meeting your favorite DJ as he was leaving. These are some memories to cherish (and not relive) once you're in a stage where sleep is first on your priority list.
That Crazy Risk You Took
Or the thing you pursued on a whim, be it dropping your steady job for a new start-up or packing your bags to start over in a different country.
Maybe it turned out to be a mistake, but didn't you know that the only failure in your 20s is inaction ? Take risks while you're young and while you can. There are invaluable lessons that come from these failures.