Treat everyone you interact with as though you are already friends. With such a welcoming approach you just never know who you might connect with, and really become your friend. Start friendly conversations with people you do not know and be kind even when your first instinct is not to be.
The next time you feel emotional, look up to the stars and try to put it in some perspective and connect with the natural world. Is it really that important? Will you remember it a year from now? Did the person who upset you do it intentionally?
"Three things in human life are important. The first is to be kind. The second is to be kind. And the third is to be kind."
Learn something new - perhaps from a friend, or join a class or teach yourself - then share it with others so they can enjoy it too.
Look for the good in everyone, even when they frustrate you. Notice their strengths and be kind when your first instinct is to be unkind or criticise - say something positive instead.
Thank your parents for everything they have done for you and tell them you love them. Most children do not realise how much their parents give up for them.