Catharsis is also known as purification. At one level, it is the first degree of the spiritual life and includes the spiritual cleansing of the body, mind, and soul. At another, deeper level, purification is about returning to our original reality in God.
In other words, catharsis is the active desire in prayer to purify our lives out of love for God or to grow increasingly closer to God through meditation and contemplation.
In it, we accept the ongoing work of ridding ourselves of as much negative influence as possible (i.e., our own sins and/or those negative things visited upon us in our lives). While this may seem difficult and even sad at first, its purpose is to joyfully cleanse us as a preparation for entering into the fullness of eternal life.
Ongoing catharsis leads us along the path into theoria and theosis, which are the second and third degrees of the spiritual life.