“A husband and wife must act with modesty in front of Hashem, even when they are alone, because there are rules of the Torah that govern their behavior. They cannot do whatever they like.”
The g’mara says that for every behavior that is assur, Hashem provides a setting that allows the individual to experience the davar ha’assur in an allowable way. For instance, for every food that is forbidden, there is a kosher food with the same taste. Having a yen for arayos? The Torah provides yibum.
Want to marry a shiksa? Try an aishes yefas toar.
How about a king like the rest of the nations? Ok says the Torah, but do it the way I tell you.
You have a desire to sacrifice animals like the rest of the world? Ok but not on an alter of one stone.
You want to have a intimate relationship with the opposite gender? Ok but get married k’halacha and keep it private.