You’ve just completed an assignment or project and you feel pretty good about it. You were diligent and thorough in your work. After you submit it, you get a response from a partner or client of an error that is glaring—so elementary and so below your capability. You are embarrassed and don’t know how you missed it. But you did.

So, how DID you miss it? Yes, you knew better, but in this instance, you only drew from one knowledge source, not two. You used your first knowledge source when you were thinking about doing it right: accounting for the rules, regulations, laws and following the appropriate procedures. It’s called procedural knowledge and your attention was on HOW to do it.

The knowledge source you didn’t use is called declarative knowledge. This source is used when you evaluate what you produced. Does it make sense? It is true? What does it all mean? Whenever you find yourself making dumb mistakes or judgments, it’s often because you accessed your procedural knowledge and forgot about your declarative knowledge.

You must be able to apply both types of thinking. While you are working, you should concentrate on getting it right. When you’ve completed your work, you need to examine it for reason, sensibility and meaning.

As a professional, you should apply this discipline with much of what you do. For instance, when you prepare an email to explain something, write it, then sit back, take a breath, and reread what you wrote. You will likely change, add or edit something that makes your intent clearer. That’s engaging both sources of knowledge.

You know how to do both types of thinking and if you apply them both, you will likely catch mistakes, errors and dumb conclusions that frustrate your clients and embarrass you.