In 2013, the Boston Celtics took a chance when they hired unproven 36-year-old Brad Stevens as the team's head coach. Since then, Stevens has helped turn the storied franchise around, taking the Celtics from the bottom of the pack to the third best team in the Eastern Conference (at time of writing).

So, how does Stevens stay focused, in a league that has been dominated by just a few superpowers in recent years? In a recent interview, Stevens summed up his philosophy in two short sentences:

"I'm not even thinking about any other team. We're trying to be the best version of ourselves."

Stevens's doctrine should hit home for most of us. It's much too easy to compare ourselves to colleagues, friends, and family members -- in respect to everything from our current job title to the type of car we drive.

But there are many reasons you should resist comparing yourself to others.

Here are three of them:

It feeds "the envy animal."

It's easy to stay positive when you cultivate an attitude of appreciation. In contrast, putting too much emphasis on others is dangerous -- because there will always be someone who's more skilled or who has more than you, at least in certain areas.

When you instead focus on your own strengths and resources, you can maximize these and be motivated to give your best effort.

The process matters.

Learning from others can be an extent. But it takes time for good ideas and hard work to reap rewards. Any success you see from friends or competitors was no doubt preceded by repeated failures and a long struggle -- much of which you're either forgetting about or unaware of.

Don't rob yourself of your own payoff by comparing yourself to others. Instead, keep your head down, work hard, and stay consistent. Good things will come in time.

You need to define success.

Remember: You need to define what success means to you.

I once had a friend whose career took off quickly. She was happy with her company, her position, and her overall quality of life -- until she started comparing herself with friends who seemed to be climbing the ladder a little faster than she was. Those constant comparisons made her really question her worth.

But a mentor advised her to refocus on the positives in her life and quit comparing herself with others. She quickly regained her joy and has thrived ever since.

While you may believe that others are doing better than you, you might not feel the same if you knew their whole situation. And in reality, their achievements have nothing to do with your happiness.

So, take time to define what's important to you. Is it doing what you love? Providing value to others? Having enough time for friends and family?

By figuring out what really matters, and then sticking to those priorities, you become the best version of yourself.

And that's what I call success.