Shaykh ibnu Uthaymeen said:
The way a person takes himself into account is by reflecting upon; what he has done? What he has left? What he has said? What he has remained silent upon? until he takes himself into account.
For example he says to himself: You did not say the truth in this affair, you did not do what’s good and right in this affair, you did wrong in this affair, you spoke falsely and untruthfully in this affair. This is how a person takes themself into account for what they did and didn’t do, so that he looks at the crookedness and remove the evil from it. This is the meaning of taking oneself into account.
Fataawaa Noor Alaa Ad-Darb (12/16)