How do I overcome recurring negative and limiting thought patterns
It's always best to talk to yourself as though supporting a 3-year-old and get rid of unwanted thoughts by using the methods of "letting them go", as described in the above two answers. If you find this negative self talk is really persistent, then besides working with a goal of saying that you are a wonderful, positive person, you could make your own meditation tape. You would need to write the words down that would specifically address the issues which are emerging, using personal, positive and present tense language. The meditative state takes you down into the Theta state, and this whole process will probably take about 15-20 minutes. It's a good way of changing habits in the subconscious mind.
An additional way is to write out in colour, positive statements about yourself and put them in prominent places around your home or working area (as long as it is private). This can be very reinforcing in a visual way.