Letting it Rest.

I don't know if anyone else has this problem.  I would LOVE some feedback on it.  So, everyone has their story, Yes.  And their physical limitations.  How do you all know when to let yourself have space and time to  rest?  How do you know when you have hit a roadblock that requires you to be a little kinder on yourself, or just an imaginary block that just needs you to bust on through?  

Personally, I am super frustrated at the moment at the fact that my body's idea of what I need to be doing and my brain's idea of what I need to be doing do not match up.  Anyone have suggestions for how to process this?

What to do when you are eating right, fully hydrated, running, yoga-ing, trying to sleep right- and still find yourself completely spent?