Do you do a great job parallel parking when no one is watching and as soon as there are people about, it takes you a number of attempts before you are properly parked?
In case you've forgotten how, you can improve your parallel parking abilities by using specific areas on your car as a gauge.
For example, whenever I parallel park, I pull up beside the car in front. I reverse straight back until my side mirror is in line with that car's rear bumper. Then, I sharply turn the steering wheel and continue reversing. When the nose of my car is adjacent to the bumper, I straighten out the wheels and voilà! my car is parked. In one attempt, too.
Next time you're parallel parking, make a mental note of the markers that will help you do a good job; audience or not!
The big benefit to parking well, in addition to a sense of satisfaction and admiring glances (maybe), is that you save your joints. The less cranking of the steering wheel and twisting of your neck and/or body, the easier it is on you.
Note: I use a similar trick when I back in to our driveway.