The “great and profound mistake which my typical man makes in regard to his day,” he elaborates, is that even though he doesn’t particularly enjoy hi… - Cal Newport

Pushing past what’s comfortable, however, is only one part of the deliberate-practice story; the other part is embracing honest feedback — even if it destroys what you thought was good. As Colvin explains in his Fortune article, “You may think that your rehearsal of a job interview was flawless, but your opinion isn’t what counts.” It’s so tempting to just assume what you’ve done is good enough and check it off your to-do list, but it’s in honest, sometimes harsh feedback that you learn where to retrain your focus in order to continue to make progress.

This focus on stretching your ability and receiving immediate feedback provides the core of a more universal principle — one that I increasingly came to believe provides the key to successfully acquiring career capital in almost any field.

Perhaps Marshall’s most striking habit was his insistence on leaving the office each day at 5:30 p.m. In an age before cell phones and email, Marshall didn’t put in a second shift late into the night once he got home. Having experienced burnout earlier in his career, he felt it was important to relax in the evening. “A man who worked himself to tatters on minor details had no ability to handle the more vital issues of war,” he once said.