As the new year unfolds — and with it the inevitable wave of self-improvement plans— Cal Newport, writing for the Wall Street Journal, identifies strategies for advancing your career.

Not all work is equal, he says. “There’s a difference between doing things you already know how to do and doing things that force you to stretch and improve your skills.” Psychology professor K. Anders Ericsson, a leader in the field of worker expertise, explains that a person in a new job usually spends some time training or shadowing someone else to get up to speed, but after that, his or her abilities tend to plateau. Beyond this point, they don’t get much better at their job, though they grow more experienced.

To get better—and to win the promotions and opportunities most of us say we want —we must set out to intentionally improve our performance. In studying why some people develop remarkable careers, this is a key unheralded distinction between the average knowledge worker and the stars at most companies: the former work hard while the latter systematically learn harder skills. Ericsson called this type of structured activity “deliberate practice,” and in his decades of research on the topic, he’s found it to be the key for expert performance in every field he has studied — from elite scientists to elite jugglers.

Here’s how to integrate this strategy into your work day:

Deliberate practice requires clarity. Set a clear goal slightly beyond your current abilities, but not too far beyond, and list specific actions that advance you toward your goal.

Deliberate practice requires feedback. Assuming you don’t reach your goal on the first try, you need a source of objective feedback so you can improve on your next iteration. Without frank, even harsh, feedback, your progress will likely stall.

Deliberate practice is unpleasant. You have to stretch yourself beyond where you’re currently comfortable — not a pleasant feeling. Most knowledge workers inadvertently end up avoiding deliberate practice-style activities because they retreat to checking email the moment a task gets too difficult. To make deliberate practice work, you must not only tolerate unpleasantness (and stick with the task, regardless of your urge for relieving distraction), but learn to seek it, like a bodybuilder seeks muscle burn.

Success in a career requires more than simply showing up early, staying late, and responding quickly to every email. True standouts systematically develop rare and valuable skills. Building these skills requires practice, and it is not something that most people seek naturally.