I love that the work I do is something that I'm passionate about and enjoy doing. In school, you are oftentimes forced to take classes that don't interest you, or forced into activities that you don't enjoy. If you find a job that aligns with your interests, you are constantly engaged in your work and actually look forward to showing up everyday.
My coworkers also make work much more enjoyable. You end up spending 40+ hours per week with them, so building great relationships with your colleagues goes a long way.
Finally, I love the independence that comes with my work. In school, you are typically constrained by a rigid schedule and (at least to me) over the top supervision. At work, you are generally given a list of items that need to be completed, and you can work on them at your own pace wherever you want as long as you get these things done (this obviously varies depending on the job). This flexibility allows you to build your schedule around your personal work habits and make the tasks at hand less daunting.