Compassion is the natural expression of the unconditioned consciousness. As you work on eliminating your defects, your compassion will naturally be freed, and expand by exercising it.
Eventually, through psychological work eliminating defects, your compassion can become a great power.
To make this more profound, train yourself daily to be attentive to the suffering of others; observe them, feel what they feel, consider how your actions affects others. Pray for help in this regard.
I also recommend studying the teachings of the great, compassionate masters: Jesus, Buddha, Krishna, etc.
“Nothing is easier than self-deceit. For what each man wishes, that he also believes.” —Demosthenes
"Do not worry; cultivate the habit of being happy." —Samael Aun Weor