Because we like people who make us feel good. Even better than good, am I right?
Unless you are offering people free gifts (do you?), you have to attract them somehow. Force is useless in the long run, so there has to be another method.
Such thing is positive energy. But not this old-fashioned synthetic smile, but true care about people around. Ask someone how to help him. Tell your girl that she looks good. It will come back to you even stronger.
Be like a farmer. Use a seed, gather a tree.