Our careers define us and we define our careers.
Every time I walk into a room I look for the exits. When I'm on a plane I try to visualize how I'll react to the oxygen mask deploying in front of me and I count the number of rows between my seat and the exit. It's part of being in emergency management and response.
My parents, both pharmacists, can easily pick out illnesses and probable treatments. I'm certain my bomb tech buddy sees potential locations for IEDs without even blinking, while my medic friends know exactly where the AED is in every room they enter and never fail to ask about allergies.
So yes, we become our careers, but I maintain that we also define our careers. We leave our mark on every project, program and person we touch. No matter what sector you choose, the impact we all strive for is an ability to take initiative and work the bureaucracy until it bends to our need.
It's what leaves a indelible mark on the job, no matter how large or small. Most people I know hope that their reputation precedes them - that someone knows who they are based on how they've defined their career field.
A friend and former boss called it, Getting Shit Done. He would say, GSD are the only initials that matter behind your name. I happen to agree. It's the definition I strive for, every single day.