For instance, was introduced to a new way of thinking about monogamy, or actually it is an old way to think about it, from the book "Assassin's Apprentice."
"Soldiers and sailors whore around. It's a common way for common folk. But not for royalty. Or for anyone with a bit of pride... It's fine to fall in love, Fitz, and no one begrudges a young woman or man a kiss or two... Traders bring pretty girls or well made youths to the market like so many chickens or so many potatoes. And the children they end up bearing may have names, but they don't have much else. And even when they marry, they don't stop their habits. If ever I find the right woman, I'll want her to know I won't be looking at another. And I'll want to know all my children are mine"
So in order to preserve your pride and to give your children a good upbringing you must be able to have self-control and temperance in your habits. Self respect and pride in yourself and your potential family.
This explanation is a less loaded than the religious explanation of "purity" as a reason for temperate behavior. In the one it is a matter of worthiness before "god" in the other a matter of worthiness of self and explanation for right behavior.
Following the rule of temperance due to self respect lends nobility to your actions, following the rule of "purity before god" lends an air of self righteous judgement to your actions. One is easy to defend, you have self respect and wish for a good life outcome. In the other the reasons may be the same but are harder to defend because the rationality is different.
I think that many things taught within religious scripts are good things but they obscure the essence of the thing making it a matter of following the rules set forth by an invisible god, rather than understanding that following certain rules or patterns of behavior will bring greater success than not.
Follow common sense principles to achieve success not a place in heaven. That certainly makes sense to me.