Every time I do a tough or lengthy cardio workout, I feel excessively tired (could sleep for hours, and I've done just that on numerous occasions). I often feel tired the next day, too, with brain fog and fractured focus.

I feel energetic and wonderful after strength training.

I've been doing fitnessblender workouts 4/5 days per week for months now. I am not sedentary, but not overly active either (stay at home mom). I have a low meat, almost no sugar, low dairy, high beans/peas/lentils and high greens diet.

I do have a heart condition called Wolf-Parkinson-White that was originally mistaken for mitral valve prolapse. Unless I drink more than one cup of coffee per day, my heart condition doesn't bother me. Not sure if this is even a contributor...

Any advice how to avoid this fatigue, or snap out of it?