Many see their 20s as an open-ended opportunity to to party, have fun, and avoid making major decisions or taking on big responsibilities. Others focus so much on getting their education and dream job in order that they melt down prematurely and promptly fall victim to a quarter-life crisis.

I'd propose a happy medium: Enjoy your 20s, but position yourself to be successful in both life and work as you enter your 30s and beyond.

Fortunately for all of us, this proposal doesn't require entering into major self-improvement programs or dedicating yourself to a disciplined silent contemplation for six months. By making these 15 simple change before your 30th birthday, you can set the stage for great personal and professional success in the years ahead:

1. Practice Using Cash

The mere action of automatically swiping your credit card or debit card keeps you emotionally detached from how much money you're actually spending. Try using cash only at the grocery store for a few weeks. You'll be surprised how much more you realize the value of money.

2. Put Everything in its Place

Clutter directly impacts our ability to be productive and stay on top of our game. Whether at home or at work, try adopting an "everything in its place" mindset. Start small, with just one or two items. Once it becomes a habit, add more.

3. Address the Small Things

Sometimes we tolerate small annoyances like a burnt-out lightbulb or a missing button on a jacket. It may not feel like much of a bother, but can actually put a drain on our mental focus and stamina. Develop a habit of addressing even the smallest issues when they occur and avoid losing precious mental focus over the smallest things that nag you.

4. Practice Gratitude

If you only choose to make one change from this list, make it this one. Each day, write down 15 things you're grateful for. Studies routinely show that gratitude improves your mental and physical health, which in turn impacts everything in your life.

5. Get Outside

Nature offers a therapeutic effect for most people, so take advantage of any chance you have to get outside and breathe in the fresh air. Take your lunch outside at work, go for a walk on your break, or spend a weekend day hiking around a park.

6. Laugh Every Day

Laughter is healthy for you and promotes relaxation, decreases pain, and decreases anxiety and stress. Not only is laughter healthy, finding things to laugh about actually helps you develop a good perspective on life. Develop a habit of laughing regularly before you hit your 30s.

7. Reduce TV and Increase Reading Time

Have a free hour in your day? Instead of turning on the television or picking up your gaming console, grab a book instead. Reading is a focused way to advance your career, develop new skills, and even improve your communication and writing skills. Best of all, it's a simple plan to follow. Read more and watch TV less.

8. Develop Leadership Skills

You don't need to land an official job as a manager to stretch your leadership muscle. You can develop leadership skills at any time by taking advantage of situations you face every day. Be flexible, decisive, and take action, and develop the ability to see the big picture.

9. Curb the Complaining

Halting your complaints and venting is one of the most powerful habits you can develop. Focus on not complaining every day for 30 days and see how rapidly your mindset shifts to more productive thoughts. You'll be amazed how much this small change can impact your daily life.

10. Feed Your Mind with Your Goals

What's the first thing you read or hear each morning? The news? Facebook? Email? Instead of starting your day with other people's priorities, develop a practice of starting your day focused on your goals and dreams. When opportunities arise, you'll be more likely to notice and take advantage of them.

11. Eat the Elephant

Do you put off hard tasks? Try a different approach instead of procrastinating and pushing stressful tasks off until later. Instead, do your hardest tasks first thing. When you arrive at work or wake up in the morning, complete the most complicated and time consuming task first. You'll feel great about your accomplishment and set the tone for productivity and success the rest of the day.

12. Don't Multitask

The importance of multitasking is one of the worst perpetuated lies ever spread. Itdamages your brain and your career by causing more distractions and less productivity. You're more likely to make mistakes and lose your attention to detail while actually completing work more slowly. Instead, pick a single task and focus on it until completion.

13. Learn to Take Breaks

Today's generation entering the workforce thinks the only way to succeed is to work non-stop. While your body may bounce back and your energy can make allowances for that in your 20s, it won't continue. By learning to take breaks, both during your day and by taking vacations, you'll be able to be successful over many years.

14. Record Your Accomplishments Each Week

Not only does recording your accomplishments help you feel encouraged about your life and work, it helps you when it comes time for annual reviews. Bosses don't see everything you do, so keeping a running list of your best work will help you get a good review.

15. Have Fun!

Life is short, and there's no reason to put off fun for "someday". Instead, make it your priority to infuse fun into your life at work and at home. But don't stop at punctuated moments of fun. Plan longer vacations and time for fun each year. When you have fun, you'll enjoy your personal and professional accomplishments even more.

What other words of wisdom would you give to those approaching their 30th birthday? Share your best tips by leaving a comment below: