What makes this achievement so admirable is that people often do this without the reward of a measurable daily accomplishment. Because of learning plateaus, it's often difficult for a student to measure forward progress by a specific achievement on every lesson. Yet, to sustain themselves, students learn by default to think in larger spans of time - months and even years in some instances. They learn to think in terms of progress, paid for in delayed gratification, which helps to sustain their motivation to achieve.
This is one of life's valuable lessons. It's the means by which we keep ourselves motivated to pursue goals of epic proportion - goals like earning a pilot certificate, building a business, landing a career with an airline.
This is one of the things that a flight student learns in addition to learning to fly. The next time one of your students graduates to the level of private pilot, remind him or her of this wonderful achievement.