Stress.

A lecturer asked an audience:"How heavy is this glass of water?" Answers called out
ranged from 20g to 500g.

The lecturer replied, "The absolute weight doesn't matter. It depends on how
long you try to hold it.
If I hold it for a minute, that's not a problem.
If I hold it for an hour, I'll have an ache in my right arm.
If I hold it for a day, you'll have to call an ambulance.

In each case, it's the same weight, but the longer I hold it, the heavier it
becomes."

He continued:"And that's the way it is with stress management. If we carry
our burdens all the time, sooner or later, as the burden becomes
increasingly heavy, we won't be able to carry on."

"As with the glass of water, you have to put it down for a while and rest
before holding it again. When we're refreshed, we can carry on with the
burden."

"So, before you return home tonight, put the burden of work down. Don't
carry it home. You can pick it up tomorrow. Whatever burdens you're carrying
now, let them down for a moment if you can."