'We simply assume that the way we see things is the way they really are or the way they should be. And our attitudes and behaviors grow out of these assumptions' ~Stephen R. Covey

Today a guy at work asked me for a post-it. I peeled a post-it off of the pad and handed it to him.
He looked confused and said.... and a pen?!!
I replied by saying, you didn't ask for one.
He said, would it not be better to just assume I need one. Wouldn't that save time?
I said, no. I don't assume anything. What if you didn't need the pen, then it wasted my time.
He went on for awhile about how assuming is the only way to move things along fast enough in life in order for it not to be painful.
I pulled off another post-it note, picked up a pen, a red pen, a highlighter, white-out and scissors and handed them to him.

I like the following quote as well...

'Guys are simple... women are not simple and they always assume that men must be just as complicated as they are, only way more mysterious. The whole point is guys are not thinking much. They are just what they appear to be. Tragically.' ~Dave Barry