I have the same thing. It is even worse, because Spanish isn't my first language, being tired just makes it almost impossible to communicate in Spanish...
A few things that I do;
Before going to bed, I take the time (30 minutes to an hour) to calm my mind from outside influences. I read, or I go to bed with the specific intention to not sleep yet, but to think and/or daydream for a bit.
(choose daydreams that are relaxing.. the other day I got thinking about sales, and selling and the excitement kept me up until way past where I wanted to be awake...
)
If it is the middle of the day, I take a 20 minute or 1,5 hour nap, depending on the time that I have.
It is enough to keep me coherent for another few hours.
Good luck!
(oh, and you might want to consider that although to you it seems very bad, it might not at all be that noticeable to others)