When stress levels get too much, you may be interested in making your own interactive punching bag. Lior Elazary wanted a sparring partner but instead built an Arduino-based circuit into his punching bag that illuminates various LEDs at various hit points instead. For example:
The use of an automated sparring partner is a simple yet useful application of the Arduino hardware, and allows for modification with regards to random or fixed punching patterns. You could also integrate timing and results measurements and even have a PC remotely recording and displaying the data. That's the beauty of Arduino, with some imagination almost anything is possible.