When you walk around closed off and in a state of suspicion, then you are going to hold back from doing a lot of things that would make others feel good, so believe that everyone cares about you and you will be more willing to take action on their happiness.

Take the time to respond to others and acknowledge that they are not feeling good, and let them get things off their chest or talk things out.

Many positive things tend to go unsaid. So give someone a sincere compliment today. It can mean especially much if it's for something that is close to the other person’s heart. Or something he or she has been putting in a good effort with like getting into better shape for the last few months.

This requires some emotional intelligence, and it is a powerful way to make other people happy. If you can recognize how other people are feeling or what they are likely thinking, then you can do things to make them happy.

This is a great rule to remember as you deal with unhappy people in any context. Put yourself in their situation and think about what you would want them to do for you.