Well, don't let one person put you down. I have sometimes had this feeling where you dread seeing somebody the next day because of something that happened, and I have found that as long as you don't think about it, you will be so much happier. Thinking about it and thinking about what it is going to be like seeing them again makes it much worse and awkward when the time comes for you two to get over it.Look at the good things in life and find out what you enjoy doing. I really enjoy reading, so for me, i would find a good book and get into it. Understand yourself and use that knowledge to keep yourself happy. Also, smile to the others around you. They will smile back, which will in turn make you happy, making you smile, making others smile and the sequence goes on... Have fun!