Why is screenprinting so hard?

Why is screenprinting so hard? It isn't hard in the sense that it is a difficult medium to learn. Screenprinting can be physically demanding once you learn the basics:

1. Always have half a cup of black acrylic paint and an equal half measure of acrylic printing medium.

2. Stir with a spoon until it has a nice runny texture. 

3. Now you are ready to print onto your watercolour paper, make sure the follow-through with the squeegee begins at the shoulders, not your wrists or hands. 

So, back to the question: why is screenprinting so hard? I refer to stamina. I think that if you print seventy-five pictures, that's a test of  your stamina. At that stage, you should perhaps take a break and return to the job in hand.

Or maybe I have little stamina? Now we'll never know....