Don't be too confident of what you know for it could be based on mis-information, dis-information, and lack of important information.

Don't be too confident of your beliefs and values for they could be based on incomplete or inaccurate analysis on your part or incomplete or inaccurate analysis you have come across and imbibed.

Don't be too confident of your words and actions for they could be based on incomplete one-sided culturally-biased analysis or wrong beliefs and values.

The less people know, the more confident people tend to become. The more a wise man knows, the more he realizes we live in a rich and complex world with new information coming to light everyday, diverse beliefs and values, and diverse justifiable actions.

Be open to new information, diverse beliefs, and people acting differently.

Be open to realizing you are wrong, and there are other equally good, if not better alternatives in almost all cases.

Be open to realizing that strong beliefs and values can make one intolerant, with a single-train of thought.

An example is most peoples strong belief in honesty. It is a commonly held and dangerous belief. There are a lot of people who desire honesty in their life without realizing it is impractical and even undesirable. How will your world look if most people were honest?

Ignorance, arrogance, and confidence have been best friends of late.

Verify your information, re-evaluate your beliefs, think of alternative words and actions.

It is this utter infallible belief in oneself - a GOD Complex - among people of power that is responsible for unpopular decisions forced top down on others.

Be open to realizing you could be wrong, and you will less likely to be so.

External links:

Neuroscientist Dr Hannah Critchlow: ‘Changing the way that you think is cognitively costly’

Dunning–Kruger effect

John Cleese on Stupidity