1. Bomb a big presentation.
"Even polished, professional speakers and public figures lay an egg now and then, and it's an important lesson to learn early: It happens, and you'll survive," says Kerr. "And you'll realize it's not the end of the world, and you'll learn a ton about what not to do and what to do next time."
2. Date the wrong person.
Whether it's the "rebound" person or just a bad choice, most everyone's done it. Discovering what you don't want early on will help you make better choices with all your important relationships, says Kerr. "It'll help you learn things about your own values and life goals that perhaps you weren't aware of."
3. Stick with a terrible job.
Even if the boss is horrible and the pay is bad, don't just give up and jump ship. Stick around for a while and try to find a solution — even if it seems like a terrible move at the time. "The way you handle yourself in this situation will forever shape the way you treat people when you're in charge," says Ryan Kahn, a career coach, founder of The Hired Group, and author of "Hired! The Guide for the Recent Grad."
4. Feel entitled, at least once.
"Assuming you were going to get that promotion or be assigned an important project or made team leader are all mistakes you should make at least once," says Kerr. "Learning from these types of mistakes will remind you to not take things for granted and to never sit back and assume something will be handed to you."
5. Hit rock bottom.
Before the wildly successful "Harry Potter" series came to life, J.K. Rowling was a single mom in her 30s on welfare, with no job, no money, and a child to raise on her own.
"I've often met people who are terrified — you know, in a straitjacket of their own making — because they'd rather do anything than fail. They don't want to try for fear of failing," she says. "[Hitting] rock bottom wasn't fun at all — I'm not romanticizing rock bottom — but it was liberating. What did I have to lose?"
6. Get fired.
If you're ever going to get fired, doing it in your 20s is the way to go, says Kerr. "Getting fired early on can be a brutally tough life experience, but it can serve as a huge wake-up call for change if there was a performance issue."
It may even serve notice that you were on the wrong career path — and better to learn that in your 20s than in your 40s.
"Being fired or laid off also teaches you the most valuable life lesson: That ultimately you need to take 100% control of your own destiny and develop the skills necessary to always have a viable back-up plan and take responsibility for your own life," he says.
7. Change jobs three times.
Sure, it won't look great on your résumé — but by trying out different career paths you'll gain insight into what your true calling is, says Kahn.
8. Take the wrong job for the wrong reasons.
It might be because of the money; it may be because you felt this was the only option at the time. But learning this lesson early will help you define your values and set you up for a more fulfilling career in the long run, Kerr explains.
9. Say whatever's on your mind without any regard for anyone else's feelings.
This is part of growing up and navigating relationships, both personal and professional. "Making the mistake of deeply offending someone can serve as a wake-up call to be more empathetic around others and help you develop better communication skills," says Kerr.
10. Burn bridges.
Obviously you don't want to do this frequently, but making the mistake of burning a bridge once or twice can actually be beneficial.
"It's sometimes more challenging to see the long-term consequences of our actions when we are younger, and burning bridges can come back to haunt us in substantial ways," Kerr says. "Learning to walk away from a difficult situation on a positive note with your head held high is an important lesson to carry with you throughout your life."
11. Go out with your friends, even though you have work to do.
"You'll always find ways to get that particular work project done, but you'll never find ways to retake that particular moment with friends," Kahn explains.
12. Offend someone with your humor.
This may not seem like a huge deal, says Kerr, "but navigating the minefield of appropriate humor in a business setting can be a challenge for people starting out in their careers, in extreme cases even costing them their jobs." Figuring out where those lines are and that everyone has different tastes and perceptions is a critically important skill to learn early.
13. Risk everything.
Risking everything for an uncertain career or romantic relationship might seem like a huge mistake to most people, but everyone should do it once early in their life. It can pay off. And if it doesn't, you will at least learn something from the experience, so it won't be a total loss.
14. Be passive.
"It's natural, especially when you're young, to sometimes sit back and want to please everyone in the hopes of making sure everyone gets along," says Kerr. "But being too passive and not learning to ask for what you want can lead to missed opportunities — and the earlier you learn that lesson, the better."
15. Think you have all the right answers.
This is a mistake you'll make over and over again your whole life. Each time, you'll be one step closer to realizing you're not always right — so it's best to start thinking this as early as possible.
16. Blame someone for your mistakes.
You should blame yourself or someone else at least once. It will help you realize this isn't productive.
"When something goes wrong, instead of looking for who to point the finger at, look for ways you can create solutions," says Kahn.
17. Think mistakes are always a bad thing or a personal reflection on you.
"Mistakes are life's feedback — they are research; they are part of your education; they are necessary stepping stones if you are actually putting yourself out there and growing," Kerr says. "If you aren't ever making any mistakes, then chances are you aren't taking any risks or trying anything new, and as you get older that may end up being the costliest mistake of all."