There are different levels on which to look at the knot or constriction at Heart level. Fear in all it's manifestations, especially fear of loss, fear of death, fear of evil, this is one aspect of the knot. To become vulnerable and let yourself be hurt by these losses, and to understand that all relationships with our loved ones end in separation, and to grieve that actively, is to loosen the knot at Heart center. To truly give others our love, in all vulnerability, to be of service, to weep,...these are tools to free the heart of it's constriction, and to learn to overcome separation. Retreats are always a time of grieving for some intangible, inexpressible, undefined loss and and in those tears, there is a joy of freedom from those bondages of Heart level. This is to loosen the constriction, though even just for a time.
On another level, what will loosen the constriction of the heart, so that it may hum with each breath, as pranic energy is free to flow past and through it? Gayatri mantra does that beautifully. So if you have fear, like the fear of being hurt, like the fear of evil entities comes to mind as I think back on a recent discussion here, then Gayatri will give you courage and protection. And that will open the Heart. Just a thought of something that has been true for me. And I have known grief, and carressed grief, not as my own, but as the shared, common legacy of our humanity.