The opinion of some is that a life of leisure and being waited on by others constitutes heaven. To these I said that happiness never consists in seeking satisfaction directly from doing nothing. If it did, we would inevitably want to take others’ happiness for our own, and if everyone did, no one would be happy. Such a life would not be active but idle, resulting in sluggishness—when as anyone can see life holds no joy unless it is active.
Angelic life consists in usefulness and acts of neighborly kindness. Nothing makes angels happier than giving information to spirits newly arrived from the world and teaching them; serving people on earth, making sure that the evil spirits present with them do not go too far, and inspiring them with good; and reviving the dead as they enter eternal life, eventually taking them to heaven, if the condition of their souls allows it.
Angels find more happiness in these activities than could ever be described. In performing them they become images of the Lord. In performing them they love their neighbor more than themselves. This makes heaven. Usefulness (that is, the good that comes of love and charity) is accordingly the substance, the source, and the measure of the angels’ happiness.
When I had finished saying these things, the spirits who thought heavenly joy consisted in relaxing and idly breathing the air of eternal ecstasy were given the opportunity to perceive what such a life would be like. The idea was to embarrass them out of it. They saw that such a life was utterly depressing and that in short order, when inactivity had destroyed all their joy, they would grow sick and tired of it.
from Secrets of Heaven, Volume 1, Section 454