"Youth is wasted on the young," according to the old saying. Why? Because in our early years we have boundless energy and untapped enthusiasm, but we also often lack the wisdom to know exactly what to do with it.

Most of us muddle through OK, but when we look back there are a few truths we really, really wish we could impart to our younger selves that would have made us happier, less stressed, or better set up for the future. What are these life lessons that lots of folks learn just a little bit later than they wished they had?

Quora is a great place to look for answers as tons of people from different walks of life freely share their experiences and wisdom on the question-and-answer site. So when a user asked "What one piece of advice would you give to your younger self?" the community responded with a gold mine of great answers.

Here are a few of the most common themes that emerged (also, guys, if this thread is anything to go on, you're really going to regret all that time wasted on video games).

1. Don't forget to enjoy the present.

When you're young, it's natural to focus on the future and working to improve your prospects. But several respondents noted that it's also easy to get so caught up in looking ahead that you don't enjoy the present. This, right here, right now, is your life. If you spend all your time with your eye on some future prize, you will miss out on an incredible amount of joy.

"Stop living in the future, and enjoy today," writes web developer Ramon Carroll in one such answer. "Yes, you can make plans, but after you make them, set them aside and focus on the thing you should be doing now, and just have fun."

"All too often we get caught up in the journey. The chase. The work. Just remember to take a moment to breathe. To reflect. To enjoy. You'll be much happier," agrees CEO Nelson Wang.

2. Being healthy actually feels good.

At 21 you might be able to down a non-recommended number of drinks the night before and get up feeling bright-eyed and bushy-tailed the next day, but very quickly you'll stop having to choose between being good and feeling good. Those two things rapidly converge as we age. Get ready for this reality by starting healthy habits early.

Systems architect James Liu would urge his younger self to "listen to what your body is communicating to you. Is your body tired? Frustrated? Unhappy? Sleepy? Maintaining a health state will give you the ability to focus your mind," he writes.

"Eat good food, sleep well, and exercise regularly, and you will always have all of the energy and willpower you need," concurs Carroll.

3. Learning is more important than schooling.

Several of those who responded essentially agreed with Mark Twain's famous quip that you shouldn't let your schooling interfere with your education. It's easy to get obsessed with perfect grades and pleasing teachers, they warn, when what you really need to keep your eye on is developing concrete skills and lifelong learning habits.

"Schooling is fine. But what matters in future is what else you learn," writes engineering student Jayant Niranjan Mundhrat, for example. He goes on to urge readers not just to chase As, but also to read and write daily, and explore the world through classes and life experiences.

4. Lean in to your fear.

In caveman days, it was a good idea to run away from the things that scared you. But today your anxieties are probably more about seeming cool or feeling uncomfortable than losing life or limb. In other words, when something scares you, it's probably because it's going to stretch your limits. That's a good thing. You should do it.

"Don't avoid the things that make you anxious," respondent Megan Walker tells her younger self. "Face them head on and conquer the fear. If you don't, you'll still have those same anxieties when you're older and it will be damn near impossible to overcome them then." Business analyst Mike Farkas is more succinct: "Risk always means opportunity."

5. True friends are hard to make and easy to lose.

Life gets busy as you get older. That leaves less time for maintaining friendships, but don't let the minutiae of the everyday distract you from staying in touch with the people who really know and love you (because honestly, in my experience, it also gets harder to meet those types of folks as the years roll by).

"Don't take the people that love you for granted," Walker advises. "Value those relationships and don't let petty stuff come between you." Developer Rahul Jain puts it this way: "Your job won't take care of you when you are sick. Your friends will. Stay in touch."

What is the top piece of advice you wish you could give your younger self?