Friendship, too, cannot be the final source of happiness (contra Aristotle), since we can't always tell our friends from our enemies. Those who are our real friends move away, drift apart, or die. Simply telling us to suppress these emotions does no good--they are too powerful to put down. These are true and deep griefs to us.
"There is no escape, then, from that misery of human life which is caused, in varying degrees, by the deaths of very close friends."
Even worse is when we see our Christian friends slip away from the faith and into sin, which is why we celebrate when believers die. "Their death, of course, afflicts our heart, but faith gives us the surer consolation, that they are now freed from those evils of this present life which threaten the best of men with either failure or defilement--and sometimes with both."
The Platonists have some idea of a "heavenly city", but they have no way to tell demons from angels, and so simply adopt all 'spiritual' beings. We, however, can discriminate between the two.
This isn't to say that we believers are never deceived by spiritual beings. Yet this just makes us long for heaven all the more. For that is where
all of our natural endowments--all that the Creator of all natures has given to our nature--will be both good and everlasting, where every wound in the soul is to be healed by wisdom and every weakness of body to be removed by resurrection; where our virtues will be no longer at war with passion or opposition of any kind, but are to have, as the prize of victory, an eternally imperturbable peace.The peace of earth is real and to be enjoyed, but it is also fleeting, uncertain, and small. When we do not enjoy it, "it is the function of virtue to make a right use of the misfortunes which we are suffering." This further turns us to the heavenly City and the coming eternal peace, which "will be a peace so good that no peace could be better, a peace so great that a greater would be impossible."
This peace is what the Bible speaks of when it speaks of heaven. Of course, we have an idea of 'peace' on earth as well, even as Christians. Even in this world we are reconciled to God and justified by faith with our sins forgiven and the process of sanctification begun. Yet we also want to be clear that 1) this only applies to Christians. Even though nonbelievers will live forever as well, we can hardly call punishment in hell 'life.' 2) Peace is what all people desire above all things, and so dwelling on what it actually means is a worthwhile endeavor.