I am retired now, but I worked as an engineer. Not only was the work mentally difficult, but I went to school for 4 years undergraduate and 5 years in graduate school to become qualified to do the job.
When people say it wasn't hard work, I just smile and point out that just the math we did makes calculus look like a Sunday School picnic.
Good for you! If we continue to teach our children common core math, we won’t have any folks like you anymore. When I got my degree, we had to complete complicated math by hand. I have helped a few people that are in college now and they just learn what buttons to push on a calculator, and what they are missing is the logic behind the math.