The first thing is that one's (own) heart is to be believed over, more than, before every other part of the body. If a troubling feeling arises from within a different part of the body such as the head, face, back, shoulder, hip, loins, butt or any part of the belly, then it should be paid attention to as something informational, but it could be either the true feeling of the way this part of the body should feel, or a symptom of one's own effect. If a feeling is really coming from your heart than it should be trusted.
So it is remarkably easy to distinguish emotions or bodily pains which are self-pitying from those feelings which are not... those from the heart are not! (N.b. I don't think self-pity is bad, but merely a technique people use, and not always a useful one at the end.) You really shouldn't outpace your heart, or sentence it to merely keeping your body alive, rather than giving it a little exercise
I also notice that the truly ecstatic emotions occur during moments one's attention is in the rhythm of the heart, and that transcendent emotions and pains emanating from other parts of the body are most frightening when they force attention away from the heart.