Fr. Garrigou Lagrange:

[A]s St. Augustine often reminds us, the same
spiritual treasure can belong in its entirety to all men, and at
the same time to each, without any disturbance of peace between
them.  Indeed, the more there are to enjoy them in common the more
completely do we possess them.  The same truth, the same virtue,
the same God, can belong to us all in like manner, and yet none of
us embarrasses his fellow-possessors.  Such are the inexhaustible
riches of the spirit that they can be the property of all and yet
satisfy the desires of each.  Indeed, only then do we possess a
truth completely when we teach it to others, when we make others
share our contemplation; only then do we truly love a virtue when
we wish others to love it also; only then do we wholly love God
when we desire to make Him loved by all.  Give money away, or spend
it, and it is no longer yours.  But give God to others, and you
possess Him more fully for yourself.  We may go even further and
say that, if we desired only one soul to be deprived of Him, if we
excluded only one soul -- even the soul of one who persecutes and
calumniates us -- from our own love, then God Himself would be
lost to us.

The Three Ages of the Spiritual Life