Hard work.
Hard work can be subjective. For some, simply walking up a set of stairs once a week can be “hard work.” for others running the Ironman twice.
Sometimes, hard work is not physical work at all. One person may find it hard to do 4 workouts a week, others may find it hard to reach out to your spouse or go up to a stranger and start talking with them.
Sometimes, one can feel that he has accomplished something in his own life by doing someone elses definition of “hard work,” but they may not have worked hard at all.
And sometimes, not being physically able to do what you could once do is hard, and the bar which measures the standard of “hard work” has moved, redifining the term hard work.
If you discovered you were going to die in a month, what “hard work” would you be glad you did? Would it be 10 workouts a day? Would it be jumping (parachutting of course) out of that airplane? Would it be meeting people that you had previously been uncomfortable with? Would it be spending time with your family?
There may be someone that can run 30 miles a day. And that same person would find talking with their children about sex, drugs, and people “hard work.” So for that person, hard work might not be physical activity at all.
There may be someone else that getting up each day, and going to work is “hard work.”
Work, from a scientific perspective is a product of force and displacement. So you could theoritically exert tremendous energy on a non-movable object, and after 4 hours and total exhaustion, have performed no work at all 
I think we would all be better people, if we developed habbits of doing things that were “hard work.” And that requires stepping out of our comfort zones, be it physically, mentally, emotionally, spiritually or morally.
