Everyday is a new challenge for many people. How you take on that challenge starts as soon as you wake up. 
Think about two things from your life that always give you a happy feeling. 
It could be kittens and puppies, or ice cream and cake. The point is to remember these things frequently.
Whenever you need to smile or feel better, calm down or relax, the first thing to do is remember your two choices. 
For me, it's rainbows and balloons. I say it every morning as a reminder to be positive. 
The great thing is that you can say it to yourself whenever you feel the need. 
Saying it out loud is even better, people always smile when I tell them rainbows and balloons make me happy. Most people want to try it themselves!
Try it for yourself. Post a note beside your alarm clock, or send yourself a message. Once you start doing it everyday, you will notice how easy it is to create a positive feeling all day.