Try to explain it in a way that you know they are familiar with such as having the flu or having really bad jetlag, when you’re hungover.
How about explaining like someone at the gym feels muscle tiredness or imaging starting your day with just 20% phone battery.
Another good way is to use the spoon theory. A story by a girl with a condition who was explaining to her friend what it’s like to have the symptoms she has.
If you explain in a way that a normal person can relate to then you have a much better chance at them understanding what you’re going through using a type of psychology and explanation of mental health