Work is play, or work is WORK. Most don’t get that.
Many spend their borrowed time doing stuff they don’t care about. I’ve reached the conclusion that there are basically two kinds of work. One which is something you care deeply about, and want to see become reality. You don’t particularly enjoy it that much. The second is stuff you genuinely enjoy. In which case, it really is play. And who counts the hours when they’re playing?
It also comes down to motivations. I mean, if you start a running habit with the sole aim of getting fit, but you don’t particularly enjoy it, then you’re quite likely to become miserable and sore very quickly. However, if the pain is something that you look forward to, if the joy of becoming better / faster / stronger than yesterday gives you a high, and if you like the challenge of sprinting up a hill even though your lungs and legs are burning in rebellion, then you’ll do it, be it rain or shine.