I do believe you can choose happiness. I have actually made a consience effort to be happy and have seen great results in business and my personal relationships.
I'm sure you have heard of it, but check out the book "The Secert." It explains what they call the "law of attraction." Basically, by controlling what you focus and think about, you have the ability to make a reality. It is impossible to be happy and have negative thoughts going through your head, the opposite is also true....it is impossible the be negative while you have positive thoughts going through your head.
Everyone reading this try something for me:
Simple smile
Now try to be unhappy while smiling!! Amazing isn't it!
You can't control anyone else and you are stuck with your family. (Every family has the person that has to complain about everything...) So you can't get rid of them; however, you can avoid negative people like the plague!
So, guess it may take work....but I truly do believe we have the ability to chose happiness.