He found that people are dissatisfied by a bad environment, but are rarely satisfied by a good environment.
In other words, what makes you satisfied is not what makes you dissatisfied. What makes you dissatisfied are what he termed "hygienic" factors: salary, working conditions, hours. What makes you satisfied are what he called "motivator" factors: the challenge of the work, the importance of the work, your impact on the organization, and whether or not the work is helping you grow.
There are some paradoxes: you can be both satisfied and dissatisfied by your job. Many nurses and teachers will understand this idea. You can be not dissatisfied but not satisfied by your job; it is not challenging and you don't find it important. Many back office workers will understand this idea. They earn a good salary and like the people they work with, but there may be a sense of emptiness.
The advice to students: choose the challenge. Start with extracurricular activities: join clubs and groups that scare you. Follow your fear: don't think you can act in a school play? Try. Might be fast enough for football, even though you aren't that big? Try.