It's very easy to get in a vicious cycle with artistic work. You have a bad day (it happens!), so you try twice as hard the next day. Instead, you end up forcing it, which backfires. Now you have 2 bad days in a row, and you try even harder, and it backfires even harder, and now you have 3 bad days.
Or, alternatively, it can become a self-fulfilling prophecy. You have a bad day. The next day your motivation is low because you expect another bad day. Maybe you don't even start working at all. That makes it a bad day, and now you have 2 bad days in a row, and with every bad day that passes it becomes harder to get back in the saddle.
So yeah, "relax, take a break" is great advice. I've had weeks during which I was just not feeling it. And that's totally fine! It's just a hobby.