'hard work' is very subjective. The vast majority of full time workers (here in Australia) work around the 38 to 40 hours per week mark. So by definition this would constitute average work and yet the majority of them would claim that they work hard. Just like almost everyone claims to be a better than average driver, so almost everyone feels they work hard. I would personally define hard work as working more than average hours or doing normal hours in a particularly unpleasant job, such as working 2km underground as a coal miner in dirty and hard conditions.