In my line of work, which is software development, there are two distinct types of people. There are programmers and there are people who “do programming”. You can probably relate that to your job, too, especially if you are in the former group for your field. Some people are the field, and others are in the field.
If you define yourself by what you do, meaning you take pride in your work, you constantly learn the latest of what is going on in your profession, and you strive to push your profession further and be –if not notable – at least respected in your field, than you are your field. That means you say “I am an X.”
If you go to work to accomplish your tasks and mentally clock out at the end of the day to live your life, if you don’t have any interest in learning or studying what you do at work outside of work, then you are simply in your field. Then you would say “I do X.” Even if you work late or come in on weekends. That just means you’re a good employee. Then you would say, “I work at X doing Y.”
The people that “do” and not “are” should be reconsidering what they do. Not only are they doing themselves a disservice because they lack the passion for their activity, but they are doing a disservice to the profession they are occupying.
In my line of work, there are plenty of people who are mediocre programmers. And they get paid quite well and can do some good things for a company. But they can’t do great things for the company. And sometimes they can do bad things by not doing great things. Think of security. If you have a good programmer at a company and a great hacker who wants to attack that company, well, you know how that’s going to end up.
In any profession, do the people in the field bring down or hold back the ones who are the field? Imagine going to the hospital and being worked on by not “a doctor” but instead someone who “does surgery.” And what about those people who actually identify themselves this way unknowingly? “I do house painting” vs. “I am a house painter.” “This is what I do” vs. “This is what I am.” It’s a big difference.
I feel I need to point out that skill and competency don’t play into this at all. There’s the sarcastic, mocking statement, “I’m an artist!”, but despite skill level, the person that makes a statement like that has passion and will do the best that they currently can. More importantly, they will constantly try to get better. They push forward out of desire where others get pulled forward out of necessity.
There’s an endless number of professions out there and the one that you really want to do really wants you to do it. They don’t want the clock-in/clock-out workers. They want champions and leaders. If everyone did what they loved, everyone would benefit.