Here is the explanation from the Catechism of the Catholic Church:
1033 We cannot be united with God unless we freely choose to love him. But we cannot love God if we sin gravely against him, against our neighbor or against ourselves: "He who does not love remains in death…To die in mortal sin without repenting and accepting God’s merciful love means remaining separated from him for ever by our own free choice. This state of definitive self-exclusion from communion with God and the blessed is called “hell.”
1036 The affirmations of Sacred Scripture and the teachings of the Church on the subject of hell are a call to the responsibility incumbent upon man to make use of his freedom in view of his eternal destiny. They are at the same time an urgent call to conversion: “Enter by the narrow gate; for the gate is wide and the way is easy, that leads to destruction, and those who enter by it are many. For the gate is narrow and the way is hard, that leads to life, and those who find it are few.”
Since we know neither the day nor the hour, we should follow the advice of the Lord and watch constantly so that, when the single course of our earthly life is completed, we may merit to enter with him into the marriage feast and be numbered among the blessed, and not, like the wicked and slothful servants, be ordered to depart into the eternal fire, into the outer darkness where “men will weep and gnash their teeth.”
1037 God predestines no one to go to hell; for this, a willful turning away from God (a mortal sin) is necessary, and persistence in it until the end…
_Catechism of the Catholic Church_
So, It’s not really so much whether you or I prefer to go to heaven or hell when questioned, or on an intellectual or academic basis. We show our desire for these ends by the living of our lives. If we would say yes to God in death, then it is most likely that we have said yes to God in our lives.
The way it was explained to me is this…If what you really love is immorality, If you are not sorry when you commit sinful acts. If you have chosen to live your life in darkness, and it is where you are most comfortable, then wouldn’t the Christian ideal of heaven, in fact, BE hell? Wouldn’t eternal presence in light, and joy be sheer misery to such a one? I’m not speaking about the addict, who is seeking with all earnestness to get well. To come to the light. Who is filled with self-loathing over the life they feel stuck in. Who ARE sorry, and repentant, but just can’t seem to figure out how to come to Jesus, and break the cycle. I can’t imagine this type being lost for eternity, because they really desire the light and God’s mercy. But what of the one we’ve all met at one time or another, who truly loves the dark side. Their idols are dark, dreary, depressing, or angry, ugly “music”. A disdain for religion. A hatred of all manner of authority, or representatives of the common good on earth. They are filled with hate. They love that which is evil and sinful, and can’t imagine why everyone else doesn’t feel the same way. They are fully absorbed with themselves. If they have any seemingly good goals, they are willing to use evil means to attain them. What evidence has this type shown of a desire to live for eternity beholding the face of God?
Though Christ was speaking to the Apostles at the time, He told them, anyway, “what you bind on earth will be bound in heaven, and what you loose on earth will be loosed in heaven”.
The idea of choosing hell, for all of us, is related to this, I believe. We are voting with our feet, our whole life through. Those with an informed conscience, who remember the difference between right and wrong, and pursue a life of right, even though they stumble, are choosing good over evil. Are saying, by their very living, that they know they were made for a better world, and can achieve it, by the grace of God. They are choosing each day to follow Jesus to the best of their ability, and when they fall short, are immediately sorry, and turn to the Lord for help.
The hell chooser could care less. They are voting for hell with their seeming absolute love of debauchery, self-indulgence, instant and disordered sexual gratification, and often these day indulgence in anti-Christian activity. Why would this type want anything to do with heaven? At least their lives don’t SEEM to ordered towards it. Do they have a shot? Well, with God, all things are possible. They can change, by making themselves open to the graces of God, but if they die in this state, and haven’t made an effort to contact Him, and tell Him they are sorry, and open themselves to His mercy and Grace, then God will not make that person do so. God loves all of us. He only asks that we love Him too. When we live counter to His will, because we think we have a better way, He’s not going to keep us from it.
Jesus comes to US. He stands at the door and knocks. If we answer, He will come in and make His home with us, but if we’re not even interested in opening the door, He’s not going to come uninvited. Not in this world, or the next.
This is how I look at it anyway.
Yes, we are all sinners. But some of us hate sin, and ask for God’s help in avoiding it. Others love sin, and don’t ask God for anything at all, except to leave us alone, and keep his disciples out of our faces. This is what I believe is meant by “choosing” hell.