My most significant firsthand experiences with 'clutch' and 'choke' come from playing touch football for many years. My claim to fame was that I had 'good hands'. I caught the ball most of the time and I sometimes made difficult catches. On the other hand, sometimes I dropped balls that were right in my hands. Anyone who's ever played receiver in football knows how good it feels to make a tough catch and how agonizing it is to drop a ball. When you drop one you go through this process of trying to figure out how the hell that could possibly happen.
Some games you just feel good...you feel strong, your mind feels sharp, you're confident...good things happen. Some games you feel like crap mentally and physically...you're 'fighting the ball', your hands don't feel quite right, when the ball is coming your way you have fears you're going to drop it.