However, in this world, love and sex have been twisted and warped. Now sex comes first, then maybe love and or pregnancy. This often does not lead to happiness for anyone, because without commitment or real caring for the other person it cannot be any other way.
The words of the song below are about the happiness and contentment that comes from someone deeply in love who, when they express it physically, are left with a good feeling afterward. It was by Engelbert Humperdinck, called After The Loving. In part:

I brush back the hair from your eyes.
And the love on your face
Is so real that it makes me want to cry.
And I know that my song Isn't sayin' anything new.
Oh, but after the lovin' I'm still in love with you.