If medieval Christians obeyed the Church on when they could have intimacy, the religion would have died out.
Even husbands and wives could only “meet” on certain days. Forbidden were Sundays, Wednesdays, and Fridays; that time of the month; during pregnancy plus a month or more after the birth; 40 days before Christmas; 40 days before and eight days after Easter; eight days after Pentecost; the eves of great feasts; and five days before Communion (maybe that’s why it was only once a year for most people).
One layman probably spoke for many when he said God gave men and women those parts below the waist so that married couples could have relations and so what if the motive was pleasure.
I’m not sure how the Church came up with its list of “no sex allowed” days. If I were a cynical person, I would say it would be a good way to drum up revenue.
If you sinned, you had to confess, then do penance, usually prayer, fasting, abstaining from meat and wine, or some combination. Or you could give alms in the form of money or land.
So while the Church could abhor relations outside matrimony and married couples meeting with each other on the wrong days, it could also make a tidy sum from the sinners.
This is why the current draft of Queen of the Darkest Hour has an uncle deciding to introduce his nephew to his favorite harlot and distract him from the queen’s maid: “Yes, it is different. You’re using a whore instead of ruining a virgin, and that’s better than making an enemy of the queen. Besides, the Church would have little funds if men did not swive whores and repent. I’ll give you some coins for penance afterward.”
Daily Life in the World of Charlemagne by Pierre Riché