Assumptions. They're risky to make.

They open up some paths of action, and close off many others.

If you choose to make assumptions, know what they are. Then check to see if you're right. You may very well be surprised.

Here's the advice others offer on the subject of assumptions and the problems they can lead to if they are not valid:

The least questioned assumptions are often the most questionable.
Paul Broca

Assumptions allow the best in life to pass you by.
John Sales

Assumptions are the termites of relationships.
Henry Winkler

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

In a start-up company, you basically throw out all assumptions every three weeks.
William Phelps

I have learned throughout my life as a composer chiefly through my mistakes and pursuits of false assumptions, not my exposure to founts of wisdom and knowledge.
Igor Stravinsky

The harder you fight to hold on to specific assumptions, the more likely there's gold in letting go of them.
John Seely Brown

And if you made assumptions that were wrong and are trying to work your way through the trouble that caused:

Don't raise your voice. Improve your argument.
Zachariah Tutu (Desmond Tutu's father)

Temper is what gets most of us in trouble. Pride is what keeps us there.
Unknown