Friends:

Unselfish Joy: How to Rejoice in Other's Success:

By seeing that:
If only happy at one's own success, such ego Joy is rare and limited!
If happy also at other's success, the Joy is more frequent & even infinite!

By observing that:
It starts with basic sympathy, develops into acceptance, genuine approval
and appreciation. It culminates in rejoicing altruistic sympathy by directing
mind to initiation, much cultivation and boundless expansion of Mutual Joy..

By knowing that:
Mutual Joy is the proximate cause of satisfied contentment!
Mutual Joy eliminates all acidic jealousy, grudge and green envy!
Mutual Joy is an infinite, truly divine, elevating and sublime mental state!

Buddha:
If it were impossible to cultivate this Good, I would not tell you to do so!

Buddhaghosa:
See how this good being is very Happy!
How fine! How excellent! How sweet!

Let there be Happiness. Let there be open Freedom.
Let there be Peace. Let there be Bliss from this.
Let there be Understanding of this Mutual Joy!



Moreover:
http://What-Buddha-Said.net/drops/IV/Mutual_Joy.htm
http://what-buddha-said.net/drops/V/Rejoicing_Joy.htm
http://What-Buddha-Said.net/drops/III/Infinitely_Joyous_Consciousness.htm

Mudita: The Buddha's Teaching on Unselfish Joy: BPS Wheel Publication No. 170
http://www.accesstoinsight.org/lib/authors/various/wheel170.html

Rejoicing Joy!