First, know exactly what you’re getting into. For example, don’t go to law school with the vague notion that “it will sharpen my analytical abilities” or “maybe I’ll get involved in politics.” Go because you want to be a lawyer, because representing clients is in your blood, because you dig argument and discovery. Go because you’ve worked in a firm and seen what lawyers do on a daily basis. Once you have a true sense of what the job requires, you can assess whether you have the stomach for its less-elevated aspects. People may gravitate to law school because they like the idea of justice, but to be a successful lawyer, you need to be comfortable with conflict.

Second, do something you not only enjoy doing and have an interest in, but that you think you may have some talent for, by dint of innate ability or life experience. A lot of folks like being around kids, but a successful teacher is likely to have a proven ability to both inspire them and channel their chaotic impulses in productive ways. He knows he has the personality to both motivate students and enforce class discipline—a delicate balancing act that many find impossible. And he has the drive to seek out training that will enhance his ability to improve kids’ lives.