I had to start the first stage in my first ever match and it was the important IPSC long course. I was so scared and stressed, my heart was pumping like hell. All i tried to do was calling my shots.
After the stage i felt like i could collapse and i really thought about driving back home. I couldn´t handle the pressure.
Somehow I made 2nd on that stage with 3 seconds slower than some of the top 5 but with much more points. Made 2nd overall in Production out of 31 and could´t believe it. I was very happy.
The next 5 matches i made many of the mistakes you talked about. Forgot targets, run targets over, forgot stage plans, shot silly mikes i called good, lost magazines and I even was laying on the ground, slipping out on a piece of brass (indoors).
It´s such a cool sport, but it´s very hard to handle the pressure