The world teaches "follow your heart".
He that trusts in his own heart is a fool: but he that walks wisely, he shall be delivered.
I believe the danger is that the feeling of happiness is the same whether we are feeling happy for being in the Church or for doing something perverted.
The etymology of "perversion" is based on exactly that per (by means of, as in) verter (turn), to turn something from where it should have turned to. When something good is used to an end that is not good, that is a perversion. So the feeling of happiness which is itself good, can be felt in non-good, perverted ways.
But if one exalts happiness as an end in itself, then whatever makes you feel that way is beyond discernement. If, worse, the fact that something makes you happy *is in itself* the measure of goodness then even perverted acts become praiseworthy.
The great scandal for this age, the stumbling rock, is the teaching that "no, it's not good or right just because it makes you happy and harms noone. Actually, you have to repent *even* from feeling happy about some things that you should not love or feel good about, if you want salvation."