Follow your heart… Trust your instincts… Listen to your feelings… You know deep inside what is right…etc
– Most people
Humans ongoingly urge and celebrate others’ trust of their ‘heart’ over their ‘head’. Why?
One explanation is that it’s just good advice. I admit I haven’t seen any research on this, though if it were true I would expect to have seen some evidence. If overly emotional people did better on IQ tests for instance we would probably have heard about it, but perhaps hearts aren’t good at that sort of question. They also aren’t good at engineering or cooking or anything else concrete and testable that I can think of except socializing. More people struggle against their inclination to do what they feel like than struggle to do more of it. Perhaps you say it isn’t their heart that likes masturbating and reading Reddit, but that really makes the advice ‘do what you feel like, if it’s admirable to me’, which is pretty vacant. Perhaps listening to your heart means doing what you want to do in the long term, rather than those things society would have you do, which are called ‘reason’ because society has bothered making up reasons for them. This seems far fetched though.
Another explanation is that we want to listen to our own hearts, i.e. do whatever we feel like without having to think of explanations agreeable to other people. We promote the general principle to justify using it to our hearts’ content. However if we are doing this to fool others, it would be strange for our strategy to include begging others to follow it too. Similarly if you want to defect in prisoners’ dilemmas, you don’t go around preaching that principle. A better explanation would explain our telling others, not our following it.
Another explanation is that this is only one side of the coin. The other half the time we compel people to listen to reason, to think in the long term, to avoid foolish whims. This seems less common to me, especially outside intellectual social groups, but perhaps I just notice it less because it doesn’t strike me as bad advice.
My favorite explanation at the moment is that we always do what our hearts tell us, but explain it in terms of abstract fabrications when our hearts’ interests do not align with those we are explaining to. Rationalization is only necessary for bad news. Have you ever said to someone, ‘I really would love to go with you, but I must submit to sensibility and work on this coursework tonight, and in fact every night for the foreseeable future’? We dearly want to do whatever our listener would have, but are often forced by sensible considerations to do something else. It never happens the other way around. ‘I’m going to stay in tonight because I would just love to, though I appreciate in sensibleness I should socialize more’. Any option that needs reasons is to be avoided. ‘Do what your heart tells you’ means ‘Do what you are telling me your heart tells you’, or translated further, ‘Do what my heart tells you’.
Meteuphoric 
A hypothesis:
Social cohesion is a result of citizens sharing a desire to believe something they all have a tiny private inkling might seem less true if they thought about it too much. They subconsciously know belief is easier when ubiquitously reinforced in social surroundings, and also that their beliefs are more enjoyable than the alternative. Thus they have a strong interest in religious behaviour in others and in their own feeling of unshakable commitment to those who practice it. So they encourage it with enthusiastic participation and try to ensconce themselves as much as necessary to feel safe from reality. If we found conclusive evidence of a god, everyone would be safe, and could get back to non-cohesion; it’s the possibility that the sky is chockers with nothingness that gives everyone the incentive for solidarity.
To test hypothesis, compare cohesion across other groups with beliefs (religious or otherwise) of varying tenuousness and of varying importance to their believers.