I'd have to say my hardest earned dollars came as a front-line healthcare worker during a global pandemic. Especially in the early days, it was scary times. We did not have proper protective gear, policies and procedures were changing literally every day as new information became available, coworkers were dropping left and right as the virus spread, and nobody really knew what was going on or what to do about it.
Later, as we got more comfortable diagnosing and treating COVID, and we got an adequate supply of protective gear, it was "better" but still grueling. Spending up to 12 hours/day in an N95 mask, gloves, and plastic gown was rough. We all had sores across our nose and on our ears from the mask eroding our skin. And we were just exhausted at the end of the day.