These words are similar and their meanings related but DON’T confuse them. Like so many easy-to-make mistakes, those errors seem especially stupid to people who know the difference.
Here’s a prime example of someone confusing the two:
What is a Guilty Conscious?
A guilty conscious is a normal human response. It’s the emotional response that comes as a result of some action that we’ve labeled, or even perceived, as being “bad” or “wrong.”
They mean “guilty conscience,” of course. And the writing seems reasonably competent but the writer leaves a poor impression of their intelligence by mixing up the two words.
“Conscious” is an adjective that means “awake” or “aware.” You become conscious (awake) when the alarm rings each day. You might also be conscious (aware) of something you did last night that you shouldn’t have, in which case your conscience (the morally-aware part of your mind or consciousness) might bother you.
How to use these two words:
Self-conscious (NOT self-conscience)
Guilty conscience (NOT guilty conscious)