In a 2017 commencement speech, Apple CEO Tim Cook dispensed some powerful advice -- not just for MIT's graduating class but for our validation-hungry society: "Measure your impact on humanity not in likes but in the lives you touch, not in popularity but the people you serve."

As Cook profoundly points out, "I found my life got bigger when I stopped caring about what people thought of me."

It's great advice, and deep down most people know it to be true -- but that doesn't make it any easier to put into practice. With instant access to metrics such as views, likes, and follows, it's no wonder people keep chasing the validation buzz.

Unfortunately, you can never get enough external approval to be happy, and you can guarantee someone will always have more likes.

Success, Tim Cook's Way

If you want to truly tap into the life-changing power of Cook's advice, you need to do more than shrug off your disapproving in-laws or stop comparing yourself with your friends on Instagram. You need to adopt a new approach to your life and fundamentally change the way you define success.

So how do you define it? That's something only you can decide, and getting to the bottom of it will require some digging.

1. Ask yourself some tough questions.

It's OK that you don't have all the answers -- as long as you have the questions. Cook explains, "As you leave here to start the next leg of your journey in life, there will be days where you ask yourself, 'Where is this all going?' 'What is the purpose?' 'What is my purpose?'" I would argue that there should be a lot of those days of self-reflection. If you're constantly reassessing your purpose, you can course-correct as often as necessary to stay on the right path.

2. Be patient and keep looking.

The answers to those key questions above probably won't appear immediately. Cook acknowledges as much, saying "I will be honest. I asked myself that same question and it took nearly 15 years to answer it." Even when the answers do appear, there's no guarantee they won't change after a while. The important thing is to keep searching, and not just in the places the people around you want you to look. That brings us to number three.

3. Step outside your comfort zone.

Try new things, even if you think they're a little on the strange side. Cook certainly didn't confine his search for meaning to any specific area: "I tried meditation. I sought guidance in religion. I read great philosophers and authors. And, in a moment of youthful indiscretion, I might even have experimented with a Windows PC, and obviously that didn't work." In our habitual search for external validation, we've become accustomed to striving toward certain things: a big promotion, a new car, or a nicer house. Giving up external validation means looking for new metrics for success based on your own self-defined purpose.

If you can follow these three steps, they'll eventually lead you to the right place. When you find it, there's just one more thing to do.

Stay the Course

People will try to sway you from your path, whether intentionally or unconsciously, but hold fast. I'll close with Cook's charge to MIT's fresh crop of college graduates:

When you are convinced that your cause is right, have the courage to take a stand. If you see a problem or an injustice, recognize that no one will fix it but you. As you go forward today, use your minds and hands and your hearts to build something bigger than yourselves.