128. This is not the joy held out by today’s individualistic and consumerist culture. Consumerism only bloats the heart. It can offer occasional and passing pleasures, but not joy. Here I am speaking of a joy lived in communion, which shares and is shared, since “there is more happiness in giving than in receiving” (Acts 20:35) and “God loves a cheerful giver” (2 Corinthians 9:7).
We brush up against the indulgence of envy. It is not a sin of the poor so much as a tragic flaw of so many well-off persons in today’s world.
Fraternal love increases our capacity for joy, since it makes us capable of rejoicing in the good of others: “Rejoice with those who rejoice” (Romans 12:15). “We rejoice when we are weak and you are strong” (2 Corinthians 13:9). On the other hand, when we “focus primarily on our own needs, we condemn ourselves to a joyless existence”. [Amoris Laetitia 110]
You can check the full document Gaudete et Exsultate on the Vatican website.