I think the article meant that there are some days when you don't have motivation to do any work - you just don't feel like it. I like arranging music for fun,

I think the article meant that there are some days when you don't have motivation to do any work - you just don't feel like it. I like arranging music for fun, but I don't always feel like it. When I do try to force myself into it, I don't get much done. The article is saying to avoid doing the work you don't feel like doing because it's going to be half-assed and not valuable anyways.