Chances are that you might click on your own ads but it can happen accidently. But you should not do this deliberately. As google has excellent tracking means to check the validity of the clicks and if they find that the clicks are not legitimate they will not give money for those clicks.
I'm surprised there are so many people who have said no! To be completely honest, I have clicked on my ad a time or two. It was right after I implemented the code and I wanted to make sure it was registering. I didn't want to wait five months and then find out I had fudged the code and that none of the ads were working as intended.
But that's it. It's not worth it to try to click on the ads on a regular basis to increase your income. And plus Google tracks things like that.