There are a couple of things that you can do to have a good day especially if you are having a bad day. Some of them include talking a way, having yoga classes or listening to music. You need to boost your positive energy by doing something you love.
Count your blessings - reflect on all the things in your life that are good, think about all the problems in the world and try and put yours in perspective, try and make yourself laugh (e.g. read a funny on-line comic or article), go for a walk - walk out your problems.
The day isn't over until it's over, are there any nice things you can do to brighten up your day later - e.g. can you call a friend or family member and catch up, read a good book, watch your favourite show, play your favourite video game?