A woman turning her husband down for sex simply because she is “not in the mood” as opposed to having some serious medical condition is a serious violation of her marriage covenant:
“3 Let the husband render unto the wife due benevolence: and likewise also the wife unto the husband. 4 The wife hath not power of her own body, but the husband: and likewise also the husband hath not power of his own body, but the wife.”
I Corinthians 7:3-4 (KJV)

Men primarily give and receive love in marriage through sex. It is what bonds them to their wife. Where as women primarily give and receive love by talking and sharing feelings and this is how women feel bonded to their husbands. This is not to say that men cannot feel bonded to their wives by talking and sharing feelings nor is this to say women don’t feel bonded to their husbands through sex. But we are talking about primary means of bonding verses secondary means of bonding which are different in men and women.

Ladies, let me translate this for you. Imagine you had a rough day with the kids and lots of other things going on at home. You can’t wait to put the kids to bed and just talk and share your day with your husband and also find out about his day. So, you get the kids to bed and slip into bed with your husband. You start talking to him about your day and he stops you “Babe, I am really not in the mood tonight” and then he rolls over and goes to sleep.

That frustration you would feel as a woman if your husband did this to you is exactly what a man feels when his wife tells him she is not in the mood for sex.