How can we define playing from the heart?

When most people describe playing from the heart it sounds like they are describing the perceived level of sincerity of the artist and his message, musically, lyrically, both or otherwise.

The word sincere is defined as lack of deceit, hypocrisy, or falseness; earnest or pure; unmixed; unadulterated or genuine.

So we can say when an artist is being sincere, the artist is actually feeling or it is perceived that he is actually feeling the emotions conveyed in his song (much like an actor).

When an artist is not really feeling the music he is writing, then he is no longer playing from the heart. I think this sincerity can also be described as keeping it real.

So now that we have a definition of what playing from the heart is… how do we do it? And how do we know that when we do it, people will still like it?

Is all music that is real and genuine necessarily good music? You must define what good music actually is.

And that can only be done on a case by case basis because it is so subjective. And from there you must determine how much of the good music is being sincere.

This is starting to get complicated, if not impossible.

Perhaps instead we can start to figure out how to be sincere then. I guess the simplest definition of this would be to make sure you feel or mean every note that you play or write.

That sounds simple enough. So why does not everybody just make sure they feel what they play?

Can we really be sure that it is truly even important to play from the heart?