Lessons to Be Learned from the Souls in Purgatory:

To abhor sin:

Especially willful, deliberate venial sin.

To shun the waste of time: 

Time is precious. It is given to us so that we may practice virtue and expiate sin. It should not be wasted in vain conversation, in fruitless reading, or in aimless occupations.

To make satisfaction for sins: 

There is a temporal punishment attached to sin. Sin, even though forgiven, must be expiated. God’s justice must be satisfied. How much easier it is to satisfy God’s justice now by voluntary penance than later in the Purgatorial fires.

To be resigned to God’s will:

To murmur, to find fault, to complain, is a sign of self-love. Love of self must be supplanted by love of God. To bear up cheerfully, resignedly, under the cross, is a true act of love of God and will serve as an efficacious Purgatory on earth.

To avoid sensuality in little things: 

To abhor little faults of vanity, of dress, of conversation, of little self-indulgences, little gratifications in eating and drinking, little manifestations of pride. The soul that constantly seeks it’s own ease, it’s own comfort, the soul that is lazy, indifferent, slothful, that shirks all painful duties and lives only for self, must be purified before it is fit to be received into the presence of God.

To abhor unkindness in thought, word or deed:

The soul that speaks evil of others, that judges them harshly, that refuses to assist them, forgets the charity of Christ and prolongs the time of separation from God.

The pious Catholic will permit the souls in Purgatory to teach him these truths and he will receive these teachings deep into the recess of his soul.

From Jesus Keep Me a 1932 prayer book.