I was half-serious about "no pain, no pain". I saw it on a tee shirt or maybe a New Yorker cartoon and thought it was pretty funny, and am a little surprised that it got serious attention. Thanks for that, by the way.
Although hard work can be worthwhile, doing something just because it is hard never made much sense to me. People that have hard lives don't go out of their way for more hardship, and many do not gain much among all that hardship.
There can be gain without pain. Hard work for some is an interesting and fun challenge for others. For example, I have never found photography "painful" or hard, just interesting and fun. Some folks do whatever they like, others like whatever they do.
Of course, there is this, which helped some people get to the moon and back to the Earth:
"We do these things not because they are easy, but because they are hard"
-John F. Kennedy, Rice University, Sept. 12, 1962