What would I do that would cause me to enter Purgatory?
Its more than just what sin, but what the state of your soul would be that could warrant this. And the simplest answer is: if you are less than perfectly clean from all sin and attachment to sin.
Let’s start with the painful truth. The only way to enter into the full glory and splendor of the Beatific Vision, thus seeing God face-to-face and being in perfect communion with Him, is to be forgiven of every sin AND to be purified of every attachment to sin. This is a glorious invitation and a demanding endeavor! Purgation of all sin and all attachment to sin is not an option.
Only when we are perfect in every way will we be ready to enter into what the saints have called “Divine Union” or “Mystical Marriage.” Think of it this way: If you are attached to sin in your life, even the smallest imperfection, that attachment cannot enter into the presence of God. God is all holy and pure love. God wants you to be in union with Him, but He will not accept your sinful attachments.
The first step is forgiveness, but that’s the easy part. God, in His mercy, will forgive us of our sins if we are sorry and ask for forgiveness. The second step is to become completely detached from all remnants of sin. For example, if you have a habit of being critical of others in your speech and you confess this, then you can be assured you are forgiven of all past sins of being critical. But forgiveness does not mean you have been purified of the “attachment” you have to that sin.
In this case, an attachment to the sin of being critical is the disordered tendency to find fault with others. An attachment is different from a temptation. An attachment is a habit you voluntarily formed. Purgation is the process of breaking every sinful habit you have and detaching from all habitual sins and even imperfections so that you can be attached to God and His holy will alone. But how on Earth do you do this? In the end, you don’t do it by yourself.
Instead, you allow God to come into your soul and purify it of all sinful habits and attachments. And that will hurt! But it will be a purifying hurt that will be freeing. Purgatory refers to the purification process of all attachments we still have when we die. Ideally, we would go through the process of purification here on Earth, before death, so as to enjoy Divine Union here and now. But when we do not complete the process here on Earth, Purgatory will complete this process after death.
It is worth restating that purgatory is not a place for “sinners”, i.e people who die with unforgiven mortal sins in their hearts. That is why they are called “Holy Souls”, because they have been forgiven of every mortal sins and are dealing with attachments to sin.