The spiritual heart is a chakra, or spiritual centre, that is located in the centre of the chest and houses our spiritual energies and propensities. Sri Chinmoy puts it this way:
"It is better to meditate in the heart than in the mind. The mind is like Times Square on New Year's Eve; the heart is like a lonely cave in the Himalayas. If you meditate in the mind, you will be able to meditate for perhaps five minutes; and out of that five minutes, for one minute you may meditate powerfully. After that you will feel your whole head getting tense. First you get joy and satisfaction; then you may feel a barren desert. But if you meditate in the heart, you acquire the capacity to identify yourself with the joy and satisfaction that you get, and then it becomes permanently yours."

Here is another concentration exercise – a creative visualisation. In this simple exercise, Sri Chinmoy asks us to image a flame inside our spiritual heart:

Kindly imagine inside your heart a flame. Right now the flame is tiny and flickering; it is not a powerful flame. But one day it will definitely become most powerful and most illumining. So every day before you pray and meditate, try to imagine inside your heart a flame, a burning flame.

And please try to imagine that that flame is illumining your mind. You cannot concentrate according to your satisfaction because the mind is not focused. The mind is constantly thinking of many things. It has become a victim of many uncomely thoughts. The mind does not have proper illumination, so imagine a beautiful flame inside your heart, illumining you. Bring that illumining flame inside your mind. Then you will gradually see a streak of light inside your mind. When your mind starts getting illumined, it is very very easy to concentrate for a long time, and also to concentrate more deeply.

Do you want to be happy?
Then do not overestimate
The power of your mind,
And do not underestimate
The light of your heart.
– Sri Chinmoy