Why Is It Necessary to Observe Family Purity?

You are right! There is no doubt that observing family purity is difficult—very difficult. Especially when there is love and a good relationship between the spouses, it is all the more difficult, particularly when they are in the same home and room. And do not think that this difficulty exists only for you; it exists for all couples who live according to the Torah and halachah, and during these days they intensely miss one another. 

Our Sages revealed to us in the Talmud what lies behind this commandment of our holy Torah. This is what our Sages said (Niddah 31b):
Rabbi Meir would say: Why did the Torah say that a woman is a niddah for seven days? Because if he is accustomed to her, he may become weary of her, so that she not become repulsive to her husband. Therefore, the Torah said that she shall be impure for seven days, so that she will be as beloved to her husband as at the time she entered the wedding canopy, etc.

Behold, the Giver of the Torah knows very well the nature of His creations, whom He formed with His own hands. Human nature is to grow weary of everything familiar—not merely to tire of it, but even to become disgusted by it. Human nature seeks renewal: to love what is new and to grow weary of what is present and familiar.

Every pleasure in our lives has a first time, which is the height of the pleasure; afterward, the pleasure gradually fades over time. God knew this very well, and therefore wished to benefit man by preserving his love for his wife, so that she would remain beloved in his eyes as at the time she entered the wedding canopy. Through the seven-day separation, a person feels longing, and thereby their love is preserved. In His great love for His people, the Holy One, blessed be He, arranged to preserve a man’s love for his wife through his separation from her during these days.

And regarding your claim that this is difficult: that is true, and it is even very difficult. We do dozens of things that are difficult for us, but what sustains us is the ultimate benefit.

And from experience, I tell you: know this!

Those who successfully maintained the separations, abstentions, and boundaries outlined for us by our rabbis preserved their homes, their love endured, and their married lives flourished and prospered. Precisely those who supposedly could not overcome their “love” found that their relationship faded and disappeared—go and test my words.

May it be His will that the Divine Presence dwell in your home, amid everlasting love.