Bill Dickinson / flickr
A recent Quora thread was full of such contemplations, originally addressed to a 23-year-old physics student but applicable to everybody.
Here are the takeaways.
1. Pick up an athletic hobby that you can do through the years. Otherwise, the sedentary lifestyle you start in college - and continue into the office - will do awful things to your posture, back, and gut. Your office job is trying to kill you. It's your job to prevent that from happening. -David Cannon
2. Write down the key points of what you did for the day. This may seem trivial, but it will show how you spend your day. Harvard Business School research shows that as little as 15 minutes of written reflection at the end of the day can make you way more productive on the job. -Stan Hayward
3. Talk to one stranger every day. Strangers = opportunity. Opportunities to make new friend, to get new ideas, to get rid of that fear of talking to strangers, to start a business venture, and much more.Who you know predicts your career, happiness, and health, so expand your network as much as you can. -Ashraf Sobli
4. Learn to listen well. People love to talk about themselves, so cultivate the ability to let them do that. -Charles Tips
5. Waste less time. Life is composed of days, days of hours, hours of minutes. And you only get so many in a lifetime. -Anonymous
6. Find happiness in the process of accomplishing your dreams. Avoid the "deferred life plan." Instead of "doing what you have to do" now and then "doing what you want to do" at some hazy time in the future, find a way to do what you like today. -Dan Lowenthal
7. Build strong friendships, and be kind to people. You're more like your friends than you think. -Edina Dizdarevic
8. Diversify your experiences. The broader your life experiences, the more creative your ideas and the better you can relate to people. -Dan Lowenthal
9. Save money. Put a little bit away with each paycheck, and do it automatically so you don't miss it. -India L. J. Mitchell
10. Drink with old people. They've been there, done that, and have lived to tell you the tale. -Ben Hinks
11. Start meditating. It trains your brain to be able to deal with the madness of each day. -Anonymous
12. Learn to work with shame and doubt. Everybody experiences these emotions, as sociologist Brené Brown has evidenced, but few people learn how to healthfully cope with them. -Diego Mejia
13. Go outside. It's easy to stay indoors all the time. So go for hikes. Cognitive psychologists have shown that a little "wilderness bathing" can be a tool against depression and burnout. -Stephen Steinberg
14. Get to know people who are different from you. If you're a liberal, make friends with conservatives. If you're part of Occupy Wall Street, befriend a banker. If you're a city mouse, get to know a country mouse. Why? Many reasons, one of them being that we make better decisions in diverse groups. -Judy Tyrer
15. Date everything. Whether you're connecting with a person, taking notes during a meeting, or stuffing takeout into the fridge, knowing the date of when something happened is useful in ways you can't predict. -Dee Vining
16. Read novels. Fiction is "emotional and cognitive simulation;" novels train you in understanding other people's experiences of life. -Anunay Arunav
17. Set minimum goals. Read 15 pages a day, do 20 pushups, floss one tooth. This way you can break gigantic projects into day-sized tasks. -Christopher Webb