Often our posture is quite poor. We slump, and it is as if our head weighs heavily on our body. Which is to say, our mind weighs heavily on our heart.
When we sit, we allow the spine to uncompress; the head is light and the torso can relax and fully breathe, giving the heart its full space.
The heart is not the seat of the emotions. Emotion is frozen feeling. It is part of the mind, not the heart. The mind is that mass of thought and emotion by which the ego perpetually talks itself back into half existence.
The heart is momentary felt experience. It is always there.