I'd say I dislike writing essays and we were set a 10,000 word one at the beginning of last term, but I enjoyed the topic so much that I could have easily overshot the word limit without noticing. I'd say that's still hard work, 'cause I still put the effort into researching and writing the essay.
If its work that needs to get done and you're being productive in the time frame given, then yes, you are still working hard even if its not hard work.
I spend a lot of time at work doing straight filing. It is mindless. I love it. But I think work would still call me a hard worker when I've sat around doing filing for two hours, because the work needed to get done and no one else was doing it.
It's a complicated question, especially for artists and writers. When you're doing something that you love or it comes naturally, it doesn't match up with the standards of 'slaving away' that we associate with work. This is why I think the question, when asked of yourself, is better termed as 'are you being productive?' rather than 'working hard.' Because if you're getting done what you need to get done and not just answering polls on DA (guilty), then does it matter if the work is hard or easy so long as its accomplished to the appropriate quality level needed?