If you recall the happiest moments in your life, they are all from when you were doing something for somebody else.
The more we think of others, the happier we are. The more we think of ourselves, the more suffering we feel.
To be happy ourselves is a most effectual contribution to the happiness of others.
Not only is your own happiness and welfare related to others, but the more you help them, the happier you will be.
One of the best ways to make yourself happy is to make other people happy. One of the best ways to make other people happy is to be happy yourself.
I do not know any way so sure of making others happy as of being so oneself, to begin with.