Read the following article and select the best answer. Article: Throughout your life, you spend the most time being with or dealing with yourself, but it is exactly yourself that you have the least understanding of. When you are going upwards in life, you tend to think too highly of yourself. When you are going downhill, you tend to have too low an opinion of yourself. It's likely that you think it wise for yourself to know your place and keep yourself from lacking courage to face whatever problem you meet with, in which case your energy and creativity would remain far from enough for your age. To get a thorough understanding of oneself is to gain a correct view of oneself and be a clear-minded realistic person-knowing both one's strength and shortage. You may look forward hopefully to the future but be sure not to expect too much, for dreams can never be fully realized. You may be brave to meet challenges, but it should be clear to you where to direct your efforts. To get a thorough understanding of oneself needs self-appreciation. Whether you hold yourself as a big tree or a thin piece of grass, whether you think you are a high mountain or a small stone, you show a state of nature that has its own reason of existence. If you really admire yourself, you'll have a real sense of self-appreciation which will give you self-confidence. As soon as you gain full confidence in yourself, you'll be enabled to fight and defeat any trouble that will otherwise defeat you. To get a thorough understanding of oneself also requires that you show yourself loving concern about your health and daily life. Unless you know perfectly well when and how to do yourself a favor, you won't be confident and ready enough even to resist the attack of illness. Therefore, just do yourself a favor whenever it's needed. In time of anger, do yourself a favor by giving an exit to it in a quiet place so that you won't be hurt by the anger itself; in time of sadness, do yourself a favor by sharing it with your friends so as to change a sad mood into a cheerful one; in time of tiredness, do yourself a favor by... Question: What's this passage mainly about? - Self-education. - Self-confidence. - Self-appreciation. - Self-understanding.
A:
Self-understanding.