You hear this all over the New Age sites, to have heart and compassion. Christ showed us and told us what we are to do to achieve compassion. And the second is like, namely this, Thou shalt love thy neighbour as thyself. There is none other commandment greater than these. Read that verse again, the very words are your clues, your truth, the way to achieve true compassion as Christ did.
Love is of the heart, thus compassion being an expression of love is also of the heart.
Yes it is simple in that the expression of the heart in its true state is love. No, refers to the process by which each of us are to get to that natural heart state. What exists now in the world and has been for thousands of years, is called separation. These cause separation in the mind leading people to think that you are not me. Thus, to truly achieve compassion of the heart requires an inner cleansing process of the mind.