"Being a graduate student is the best." - Wallace Marshall
You have no responsibilities other than to follow your heart and find the type of science you are most passionate about. You utilize the university setting to take fun classes (drawing, storytelling, improv) and marvel at the fact that you are now trusted to teach the next generation (who, after all, are only a few years younger than you are). You collaborate with and are constantly sheltered by your advisor. With a 1-minute commute to work, and having just received the biggest pay raise of your life (from paying for tuition to being paid for your services), your life is unbelievably amazing!
"Being a postdoc is the best." - Wallace Marshall
Postdocs know everything. Seriously. Tell any postdoc about your work, and they will suggest several relevant papers. They ask deep questions during group meetings. They know most aspects of their work better then their advisor. Clearly, at some point between the end of graduate school and the beginning of their postdoc, every scientist becomes orders of magnitude more knowledgeable. It is likely a gradual (and hence unnoticed) transition, but it definitely happens.
But postdocs are also cautious. Most are hesitant about committing themselves to academia, since there are many more outstanding candidates than there are positions. Some go into industry, while others stay in school forever. In either case, it is incredibly exciting to see someone you met as a postdoc move on to bigger and better things!
"Being a professor is the best." - Wallace Marshall
Professors are incredible. They know everything and everyone. They are the top of the food chain, leading the charge on important problems. Yet when asked what their favorite part of their job is, every professor will tell you it is seeing their students grow and succeed as scientists in their own right.
Professors have the honor of teaching as well as convincing other scientists that their work is revolutionary. They have great control of their lives, and they take a year-long break every 7-ish years to reinvigorate themselves, reflect on what their lab has accomplished, and reorient their goals to better match their passions. They have the privilege to lead a tight-knit group of incredibly talented individuals to tackle problems that no one in the world knows the answer to. And that is, unquestionably, the coolest job in the world!