Life is a constant stream of events and those events come with choices. The biggest choice being the one dealing with attitude.
Some things are easy. They go well, lift you ten feet off the ground emotionally and you go through the moment naturally elated.
Other things are a bit more complex. Things don't go the way you wanted them to, they present a set of challenges, or flat out slap you across the face with a completely unexpected/unwanted outcome. Andeven at these times, though less natural, a positive attitude is still possible.
I've been listening to Randy Pausch's book about his Last Lecture and in it he repeats, "Experience is what you get when you didn't get what you wanted."
It's true and representative of a larger notion. There is always a positive to be found. It just requires training your brain to find it - to look for it.
I truly believe that most of the time you'll find whatever you are looking for. So if you focus on bad things you will see only bad, but if you look for the good and keep a positive frame of mind - positive aspects will start coming your way.
Look at "bad" and difficult things in your life and figure out how you can grow from them or how they could later benefit you. Find the experience, the lesson, the unexpected positives.
It's no different than taking a good photo of a scene or an object that a million people would never see beautifully - or would simply walk by and never take a second glance at at all. You've got to frame and reframe until things look the way you want them to.
So, reposition events in your mind until you see what you need to see. Look at them harder. Turn them over. Tilt them. Flip them around.
And, find the positive. (It's always there for the taking!)