there is endogenous morphine in the placenta too.
does that mean god makes all babies smack addicts?
there is nothing wrong with pleasure in fact the more relaxed you are about pleasure the more pleasure flows to your body. it is our natural god given state. but people tend to get a bit grasping about the slightest pleasure in their bodies. so desperate are we that it never leaves, we don't breath properly and it begins to fade. that's why many people tense up before an orgasm( shock horror). the same is true of pain. our deeply held aversion to gross solidified sensations makes us tense which ,inversely, greatly intensifies the pain.
if mind can be focused on pain with equanimity it will break it down into lots of little sensations and disperse it. this is mind and matter in harmony.
we are not meant to ignore or press down our god given biology(what is evil in a chemical process?) but to understand it. instead most of us play a game of craving and aversion which is entirely about mind. thusly we never fully experience our pleasure and intensify solidfied sensations.
the nature of sensation is impermanence. trying to evince subtle sensations with outside agents(including sex for the sake of the sensation alone) is harmful. this is how addictions arise. every time we do this it makes it that much harder to retrain the mind. if the body is well it produces those sensations naturally but all sensations to be witnessed and accepted as they arise.
consider how many rotten choices we make for ourselves because it will give us comfort in the short term. how ironic then that we have our own endless supply of endorphins.