Earlier that year, he'd raised thousands of dollars for his start-up, going to heroic lengths to do so, and pulling several all-nighters in the process. I was impressed and said so. But I hastened to add that grit is more about stamina than intensity.

To be gritty is to keep putting one foot in front of the other. To be gritty is to hold fast to an interesting and purposeful goal. To be gritty is to invest, day after week after year, in challenging practice. To be gritty is to fall down seven times, and rise eight.

We all face limits—not just in talent, but in opportunity. But more often than we think, our limits are self-imposed. We try, fail, and conclude we've bumped our heads against the ceiling of possibility. Or maybe after taking just a few steps we change direction. In either case, we never venture as far as we might have.

And, finally, intellectual character includes virtues like curiositv and zest. These encourage active and open engagement with the world of ideas. My longitudinal studies show these three virtue clusters predict different outcomes. For academic achievement, including stellar report card grades, the cluster containing grit is the most predictive. But for positive social functioning, including how many friends you have, interpersonal character is more important. And for a positive, independent posture toward learning, intellectual virtue trumps the others.

Interpersonal character includes gratitude, social intelligence, and self-control over emotions like anger. These virtues help you get along with and provide assistance to other people. Sometimes, these virtues are referred to as "moral character." David Brooks prefers the term "eulogy virtues" because, in the end, they may be more important to how people remember us than anything else. When we speak admiringly of someone being a "deeply good" person, I think it's this cluster of virtues we're thinking about.

Intrapersonal character includes grit. This cluster of virtues also includes self-control, particularly as it relates to resisting temptations like texting and video games. What this means is that gritty people tend to be self-controlled and vice versa. Collectively, virtues that make possible the accomplishment of personally valued goals have also been called "performance character" or "self-management skills." Social commentator and journalist David Brooks calls these "resume virtues" because they're the sorts of things that get us hired and keep us employed.