Like a violent lightening bolt, a positive attitude can cause a chain reaction that just might make someone's day a little more tolerable, prevent someone from taking their own life, persuading another to say a kind word or do a sincere deed. It's also contagious so spread a positive attitude and give someone a compliment, say a prayer for someone you barely know,etc .
Even in the class, during lecture, each student's smile will give a good chain reaction to the lecturer to deliver a good lecture. Vice versa...
Give it a try.... :)