Like others have said, enjoy your trip and don't obsess about what could go wrong. I just want to share my experience so that you can learn from it.
I was on the Charles Bridge last Saturday (Sept. 6th. 2014). I had noticed a certain individual. First he was "praying" on the bridge, and then later I saw him "praying" in a narrow busy walking street. Later that same day, I noticed this person (dressed in camo clothes, and redish hair) stumbling across Charles bridge. I watch him bump into several people, my wife included. I decided to follow him. When I did, I later say him stand up straight and talk with a friend of his and then kneel down to a praying condition. Basically, I think he was pretending to be stoned / drunk, but was trying to pickpocket people. After watching these guys for a few minutes, I made my way back to our hotel, my wife told me that when I started following the first guy, the “friend” started following me. And also, the first guy actually circled back and bumped into my wife a second time.
So basically, just want to let people know that these guys work in teams, and to be careful. Safe travels to all.