Serving others is our greatest source of happiness. It is always a sacrifice big or small when we give ourselves and our time to others, but with a sacrifice something is always gained. A sense of peace and wholesome happiness comes when we are in the service of others. A greater happiness is gained when a greater sacrifice is given.
"But this I say, He which soweth sparingly shall reap also sparingly; and he which soweth bountifully shall reap also bountifully", 2 Corinthians 9:6. That scripture rings true to me. As my dad would say, "You get what you put it into it." To have happiness, serve others.