Its a bit like the spoon one but its better.

So, there is a really good article on something called “Spoon Theory” google it, which is a very relatable way of explaining what its like with a chronic illness to somebody without one. However, I swear by a hybrid of this called “Fork Theory”. I’ll explain the spoons bit first to give you an idea and then hopefully you will understand fork theory better.
Imagine a normal person throughout their day has a unlimited supply of spoons however throughout their day everything they do costs spoons. You get out of bed, brush your teeth, have a shower and get dressed, well that costs 2 spoons. You drive to work and that’s 2 more, 1 more because there was a traffic jam. Already that has cost you 5 spoons and you have only just sat down at your desk.
  Your first task of the day involves a lot of spreadsheet work and maths where you have to think about things in detail and that’s going to take till lunch, well that’s 5 more spoons. Lunch is an hour where you carry on working at your desk eating a sandwich then its more spreadsheets and then at the end of the day a delivery comes that nobody is there to deal with it and its heavy. That afternoon has cost you 10 more spoons. Days total so far is 20 spoons.
Drive home in rush hour, 3 spoons, cook dinner 3 spoons, washing up 2 spoons, carry on working on your spreadsheet 5 spoons.
Daily total 33 spoons.
Now imagine you are a person with MS for example, each day you get given only 25 spoons and you have to spend them wisely otherwise when you run out you resemble a puddle of slime on the floor unable to move until the following day when you have slept and got your daily spoons back. If we would use those 25 spoons on the day we spoke about by lunchtime you only have 5 spoons to last the entire afternoon and evening. Basically, you are not getting through your day.
This is where I use fork theory, its technically the same but you can spend forks to gain forks. This is why I do things like go to my body balance class or go swimming. I know that will cost me 2 forks to do that but by spending 2 I will then get 5 back and balancing this correctly results in me being able to make it to the end of the day pretty normally.
Get it wrong however and I’m that puddle of slime I spoke about earlier and there is no point in trying to spend forks to get forks as you don’t have them to spend in the first place.
Things I spend my forks on to get more back include :- 
Swimming, Cycling / Spinning, Body Balance class, Yoga, Power naps (5 / 10 mins will do), Taking a break usually to do one of the above) or just not being on your feet.
I can always tell when I’m running out of forks as I get brain fog, my limbs feel clumsy and I bump into things and my speech gets a bit slurry. This is usually the time where I have to consider my recharge strategy or to start rationing forks to what I still need to do that day.
Hopefully this will help you & at least give you a way of explaining your situation to others.