We are only human: As hard as we try to continually cleave to That Which is Eternal, there is always that Spiritual Entity that Hashem created as a counterforce specifically to tempt us away, pulling us down into the murky swamp of mundaneness (Tumah). King Solomon called it an Old Thoughtless King (Koheles 4 13); our sages called it the Yetzer Harah; and the Kabbalists call it by its spiritual roots - Samech-Mem. These two Hebrew letters are also the root of the word blind - Suma, and rightly so, for that Counterforce has a weakness: Being so geared towards superficial goals, it can be 'bought off' very cheaply with small immediate gains. By telling ourselves, "If I do this big Mitzvah, I will allow myself to indulge in such and such (permitted) physical pleasure", we fool It into overlooking our longlasting benefit in order to acheive It's miniscule momentary gain.
Our Parsha teaches us another important use of this vulnerability that we use on the Holy Day of Atonement: Teshuva - returning to untaintedness, requires a change of outlook. When we perceive the world from the vantage point of Eternity, we regret our excessive involvement in profane matters and aspire to live holier lives from now on. But where does the whole Jewish Nation get such elevated feelings on this special day? The answer is that Hashem gave us careful directions how to connect to Divinity and bring down this inspiration. Although Nadav and Avihu lost their corporal existence by reaching spiritual heights that their physicalness could not endure, one can attain such heights by 'paying off' the Samech-Mem with the appearance of bringing it sacrifices. After bringing all the sacrifices to Hashem on Yom Kippur, the High Priest singles one out at Hashem's behest and seemingly 'gives' it to the Force of Destruction. He can then bring down a pure desire for closeness to Hashem to the whole Jewish Nation by emulating its spiritual source by putting the holy incense (Abba - Chochma) on burning embers (Imma - Binah) in the Holy of Holies (Lifnim min haPargod).
Although we unfortunately don't have sacrifices today, there are still certain righteous individuals who are familiar with all the intricate details of these holy intentions (Kavanos) and utilize them every Yom Kippur to instill us all with elevated aspirations.
Based on Rabbi Vali's book on Vayikra. Questions can be mailed to: the Yeshiva