A story that i barely remember

I was reading Starlove's entry when i decided to leave a comment.
This comment made me remember a little story i read somewhere, so i'll type it down below.

Not exactly what i read, but you get the gist.

Picture a glass cup.
Would it be heavier when its full? or half full?
How long would you be able to hold it if its full, and how long will you be able to, if its half full?

The question here is that it doesn't matter how heavy the glass is.
When you have to realise is that a burden, no matter how light or heavy it is, will slowly become unbearable if you don't set it down.

When it gets too heavy, remember. Put it down and rest and recharge, before picking it up again. You'll find that its much lighter.