"if it feels good, do it" is particularly consequential when it comes to procreation. That's one reason why it's so devastating. It's one thing for our desires to take on a godlike force in making decisions in our lives. But when you combine that with or apply that to sexuality, which of course centrally involves the reproductive system, you end up procreating new people. And if a person is created into a situation where his or her parents are not able to wisely and appropriately raise that child, then far more problems are created then were solved by the initial sense of "if it feels good do it."
Following one's desires is risky at best, but if it is practiced in other areas of life that do not result in a brand-new person existing where they did not before, then the damage is generally more limited. Because sex is centered around the reproductive system, The consequences of actions in that area are of life and death. Generally speaking, contraception tends to mask this fact. Through the use of contraception, people tend to assume that they have control over the process, and therefore can ignore the fact that life and death are at stake, that real people can come into existence through actions involving this area of life.
The secularizing of society, which tends toward seeing people as not complete, divinely inspired souls, but merely physical bags of desire, contributes to this. It tends to suck the hope out of a life, so that all we strive for is the fulfillment of our desires, and we believe that that's all that there can be. And then, on top of emptying our own lives of meaning and value, it then makes it easier to believe that children who are procreated (and then sometimes destroyed through abortion) don't have an intrinsic, enormous value that needs to be preserved or taken care of.