Among other things, a good indicator to take a break is when you start questioning the validity and effect of what you are doing.
It will start small with "does even writing help me?" and can escalate fairly quickly to "will my job even exist in a year?"
Questions that are important, but asking them in that moment brings no value other than making you stay still and messing with your consistency.
I have found that questions like that come when I have overwhelmed myself with different projects and set unrealistic expectations for their delivery.
I cannot win them. I just take a break, even for the whole evening, and resume the next day.
Hopefully they come once a month or so.
Because if they came every evening, they would probably be interpreted totally differently.
The doubt isn't telling me something about my path. It's telling me something about my pace.