Have you ever had a bad day just because you crossed paths with someone who was in a foul mood? Maybe it was someone on the bus or another customer in a store—someone who you normally wouldn’t have even noticed—but that one grumpy or inconsiderate person cast a pall on your whole day.

On the other hand, have you ever had a day that went great and realized later that it all started when you met someone who was especially nice to you? Maybe it was the way she smiled at you, or the way he picked up and handed you something you had dropped, or held a door open for you—only a little gesture, but one that had a positive impact on your day.

Everyone has influence. Moment by moment your attitude and level of happiness are reflected in the little things you say and do, and those are bound to affect others. What kind of impact do you usually have?

Think of the things people have done that made your day, and make a point of doing those same things for others. Not only will you brighten someone else’s day, but you will also find that you are happier and see life more positively.