Even if we examine ourselves, our experience tells us that we still cannot know ourselves. Let us see what the Bible says about us.
Jeremiah 17:9 says: "The heart is deceitful above all things / And it is incurable; / Who can know it?" Since our heart is deceitful, our self-examination will not be reliable. Because we are using a deceitful heart to examine ourselves, we cannot avoid being deceived by this deceitful heart. Perhaps you are wrong, but your heart may tell you that you are not wrong. Or perhaps you are not wrong, but because of some weaknesses, your heart may tell you that you are wrong. If the heart were proper, then it could be used as a standard; but, since the heart is deceitful, how can it be used as a standard? If you use an inaccurate standard to examine yourself, surely it will be hard for you not to be deceived.
A man was installing a chimney, and after he measured it with his ruler, he told the metal worker to make it ten feet long. When it was finished and delivered to him, no matter how he measured, it was one foot too long. He complained to the metal worker, and the metal worker measured it with his own ruler. It was exactly ten feet. However, the installer insisted that it was one foot too long. Eventually, the metal worker looked at the man's ruler and found that one-tenth of the man's ruler had been sawed off by his son who had played with it. Therefore, the chimney always measured one foot too long. If we would examine ourselves, we must first ask whether or not we are trustworthy. We have been corrupted and in the sight of God are very evil. How can we examine ourselves? Many think that self-examination is a virtue. But let me tell you: self-examination is a big mistake.
We have to know that the structure of our inward psychological parts is complex. Our desire, thought, feeling, and other manifestations of our heart are very complex. We cannot clearly analyze how they influence and interact one with the other. In such a complicated condition, even though we can examine ourselves, self-examination will never give us accurate self-knowledge. While you are examining your feelings, you do not know how your feelings are affected by and connected with all the other areas. Therefore, knowledge gained from your feeling is not trustworthy. Only a little influence can change your feeling completely. Many times concerning a certain matter we lose the proper view and do not have the accurate knowledge regarding our own intentions because there is a little hidden sin, wrong thought, or little prejudice inside us or because of our disposition by birth and innumerable other little causes. Any knowledge which we derive from ourselves is inaccurate because it is so complicated and untrustworthy.
We often come across a situation in which a person is very good on some point but does not know it; rather, he feels that he is weak on that point. On the other hand, he is weak on another point, yet he does not realize it but considers himself to be very good on that point. We often see this. This shows us that, even though man may examine himself, it is still impossible for him to know himself. Man cannot know himself through self-examination. I have a friend who talked very much about Christian love after he was saved. According to his view he considered himself to have much love, but in his home he was not at peace with his wife. Think about it! If one wishes to examine himself, is his self reliable? If his self is not trustworthy, then examining himself is useless.
Psalm 19:12 asks, "Who can discern his errors?" No one can know. We cannot know for sure our errors by ourselves.