A duty to ourselves

With the Feast of Our Lady of the Angels coming up this weekend (August 2nd) and the attached indulgence, The Portiuncula Indulgence, I have started my Examination of Conscience in preparation for confession tomorrow night (with the kids and all, I have to plan ahead instead of doing my examination as I'm on my way to confession!). I always like to take advantage of God's great mercy because I shudder to think of the time I will spend in Purgatory. Eyes have not seen and ears have not heard what God has in store for us in Heaven, but Purgatory might be a corollary and conversely, equally horrible. If we only saw the effects of sin as God does, at least to the extent that we could withstand...

NB: One is not required to attend Mass on the day of the visit to a church. See posts here and here. (Thanks for the clarification, Terry)

From The Spiritual Life, by Adolphe Tanquerey SS, DD:
Sin leaves in the soul baneful consequences against which it is necessary to react.
A.) Even when the guilt or fault has been remitted, there generally remains a temporal punishment varying according to the gravity and number of our sins, and according to the fervor of our contrition at the moment of our return to God. This punishment must be undergone either in this life or in the next. By far the most advantageous course is to make satisfaction in this life. The sooner and the more perfectly we acquit ourselves of this debt, the better fitted our soul becomes for union with God. Moreover, expiation on earth is easier, since this is the acceptable time for mercy; it is more fruitful, since the acts wherewith we make satisfaction are also meritorious, a source of grace and greater glory. Therefore, personal interest and love for our own soul are best served by a prompt and whole-hearted penance.
B.) Moreover, by the fact that sin intensifies in us the disordered love of pleasure and weakens our will, it bequeaths to us a pernicious facility to commit fresh faults. Nothing so well rectifies this disorder as the virtue of penance. By having us bear with fortitude the afflictions and austerities compatible with our health, it gradually weakens within us the love of pleasure, and inspires us with a fear of sin which exacts such amends. By inuring us to the exercise of such acts of virtue as are opposed to our evil habits, it helps us to correct them and thus gives us greater security for the future. Hence, to do penance is charity towards ourselves.
The Spiritual Life, pp. 356-357.