The word dark for many stirs up feelings of anxiety and uncertainty. It is a time when evil lurks as the passuk says (Tehillim 104,20) בו תרמש כל חיתו יער . However for others who love chocolate and need to stay pareve, the word dark conjures up feelings of pleasure. There is an expression to "be in the dark" which means not to know and realize enough information or facts to understand what is going on in a particular situation. For some individuals the not knowing creates FOMO and frustration, together with feelings of losing control over oneself. Yet many a time to be in the dark can be a plus to protect and save one from falling into something worse if you actually found out what you were seeking.
One such case is spot of tzaraas found present on the inside wall of one's dwelling which can result in the house being completely razed to the ground. Chazal say (Sanhedrin 92) comment on the passuk כנגע נראה לי בבית like a leprosy appeared to me in the house. This teaches that a tzaraas spot appearing in a darkened house where the spot cannot be seen properly by the sunlight that shines in, is disregarded. For the lashon of "appeared" conveys by natural lighting. However to examine it by opening a new window opposite the spot is not required. The word to me also indicates to exclude my examining the negah spot with the help of my lamp. In this situation as well the spot is disregarded.
What emerges from this halacha is that the house's lack of light is what saves it from destruction even though an authentic spot of tzaraas is actually in his house. The Torah is suggesting that sometimes it is more beneficial to turn a blind eye instead of addressing the issue at hand.
In that same gemarah Rabbe Elazar says לעולם הוי קבל וקיים that a person should be humble and stay in the dark (out of the limelight). By doing so he will have a long life. The Maharsha explains for one who flaunts his talent and wealth will arouse jealousy and bring an ayin harah upon himself. Rav Zeirah comments that this yesod of Rabbe Elazar is derived from the above Mishnah dealing with a spot of leprosy in a dark house which protects him from losing out. Interesting that the word dark contains the word ark. It was an ark that saved him and the future humanity from utter annihilation. So too darkness can sometimes save one from losses.
One of the reasons that tzaraas strikes a person is because of speaking Lashon Harah. The individual who listens to the lashon harah is also a sinner. Chazal teach that the listener is often worse, because without a listener, the speaker would not speak. One must stop the speaker, leave the conversation, or ignore the comments if leaving is not possible. This Mishna is advising the "hearer" to remain in the dark even though his curiosity of listening to the juicy story is seducing him to choose an immoral conduct which will chas veshalom harm you.
Another example of turning a blind eye to the point of even deliberately putting yourself in the dark is with Shalom Bayis. In the sefer Toldos Yitzchak the uncle of the Bais Yosef, it says that in the creation of Chavah the passuk writes
ויפל ה' אלקים תרדמה על האדם ויישן ויקח אחת מצלעותיו ויסדר בשר תחתנה
Hashem caused a deep sleep to fall upon man and he slept. Why did Hashem have to place Adam under a deep sleep in order to create Chavah? He answers
רמז שהאדם יעשה עצמו נרדם בביתו ולא יהיה קפדן עם אשתו ובני ביתו
It was a hint to Man that he should not be a קפדן in his house, to his wife nor to his family. In essence the husband must not be too critical to his mishpacha calling them out on every little thing. A קפדן refers to the individual who must be right always with no flexibility to say "let's imagine that I am in the dark and I can overlook a negah tzaraas an imperfection here and there". Rather the approach should be that some time he should choose to turn a blind eye as if saying to himself I was sleeping and didn't see that or hear that negative remark. Of course, it depends on each particular situation and requires saichel. Note that the English word negative has within it the word נגע and טיב. One has the bechirah to focus only on negative behavior with the response of chastisement or he can turn a blind eye and see the offender in a positive good light as if he didn't do any transgression.
An allusion to this disciplined behavior of not being too critical can be gleaned from the passuk ורוח תשימו בין עדר לעדר (Bereishis 32,16) place a space between the flocks when you give my gift to Aisav. The word עדר can also be interpreted as a lack - העדר. When one is confronted with a family member's lack and חסרון and feels it has come time to reprimand this individual, he should first reckon with his "accountant" and check if he has already fallen into the category of being a קפדן and used up all his credits for that day or week. To this concept the passuk alludes that one must remember to place a space between your barrage of corrections by graciously sprinkling some positive words in between once in a while. This is what the word רוח also means – profit. One must always acknowledge gains achieved by the person who is given criticism in order to demonstrate that he still has worth, value, and endearment by you.
Many a time the offender knows that you could have gone ballistic at him or her and yet you controlled yourself and let it fly by so he or she could save face. This investment into the emotional bank of relationships is a humongous deposit and also serves as a learning experience for the wrongdoer. It could change the letters of נגע into ענג pleasure. By making yourself to "be in the dark" it can save your house and family relationships from deteriorating and being torn down. Work towards Raising your mishpacha instead of Razing them.
Moshe entered three layers of darkness in order to speak and hear Hashem at Matan Torah (Devarim 4,11) חושך ענן וערפל. The passuk says (Shmos 20, 18) ומשה נגש אל הערפל ושם האלקים. The gematriah of הערפל the thickest darkness is שכינה . You will then merit to see beracha nachas and shalom bayis together with the Shechinah.