Mental exhaustion vs burnout.

What's the difference? I don't truly remember if Sarno applies the mental exhaustion in his "Healing Back Pain" Book, but I would like to recover from mental exhaustion.

symptoms:
Can't think straight, have mindfog, have struggle talking due to thinking, I feel like taking naps and more.

I'm 6'1-2'' weight 154, I workout bodyweight atm around 3 times a week.

I truly don't know how it feels to feel stressed, but should I keep the practice of Sarnos when it comes to OCD, mental exhaustion and burnout?

Also it seems when I exercise and push myself it can be worse.