In "The Problem of Pain" C.S. Lewis writes,
It may be that salvation consists not in the cancelling of these eternal moments [moments of sin] but in the perfected humanity that bears the shame forever, rejoicing in the occasion which is furnished to God's compassion and glad that it should be common knoweledge to the universe. Perhaps in that eternal moment [even] St. Peter - forever denies his Master. If so, it would indeed be true that the joys of Heaven are for most of us, in our present condition, 'an acquired taste' - and certain ways of life [sins committed] may render that taste impossible of acquisition. Perhaps the lost are those who dare not go to such a public place.
I find this view of heaven and hell quite insightful because in emphsizes "our" choice in whether we experience eternal bliss or eternal torment. It is true that both heaven and hell are filled with sinners. However, as Lewis points out, those in heaven are the ones who are not afraid to face their sins. They are glad to have them exposed so that they may learn from them and move beyond them.
The alternative is for those who attempt to cover their sins. In essence, they deny their wrongdoings and attempt to hide their shame. They cannot come to terms with the evil they have done and fear that they will be exposed. In this way, they hide in the darkness where even more evil can grow. It is no wonder that when faced with a future in a place of pure light and love, such people prefer the outer darkness.