It costs nothing, but creates much.

It enriches those who receive, without improverishing those who give.

It happens in a flash and the memory of it sometimes lasts forever.

None are so rich they can get along without it, and none so poor but are richer for its benefits.

It creates happiness in the home, fosters good will in a business, and is the countersign of friends. 

It is rest to the weary, daylight to the discouraged, sunshine to the sad, and nature's best anidote for trouble.

Yet it cannot be bought, begged, borrowed, or stolen, for it is something that is no earthly good to anybody until it is given away.

And if at the end of a long, long day someone should be too tired to give you a smile, may we ask you to give one of yours. 

For nobody needs a smile so much as those who have none left to give.

-Author unknown