reacting with tiredness to stress and seeking sleep during the day – ways to get out?

I am stuck in a vicious cycle. My schedule is very tight and challenging and I often get quite stressed. This for example happens when a task takes much more time than anticipated. As a reaction, I can get very tired. After sleeping for an hour or more in the middle of the day I I feel energy again but then, of course, I am very much behind in my schedule what results in even more stress.

Is my brain possibly tricking me into this tiredness to get me away from the challenging work as a way of buffering? How do I tell the difference between a true need of my body and my brain manipulating me? Also, is there something I could do to resist the tiredness like a mantra or a ritual? Or, if resisting it is not wise at this moment, what do you think about planning one hour of siesta into my schedule?
I feel that I am sleeping too much though … 😀

I hope you can give me a clue here, thank you so much!