I voted "1 in about 20" because by my best guess I've killed between 20 and 40 animals and have lost one. I'm hoping the 1 in 5 and even 1 in 10 guys are voting based on a smaller number of animals taken, not a lifetime of 80 or 90% recovery rates.
Due to the places I hunt and the way I go about it, opportunities are often very short lived. There's generally not a ton of time to sit and stare at an animal, evaluate the situation over and over and over in my head, think about all the little details that could go wrong, etc. The lack of time to get nervous helps a lot...from the time I spot an animal until I pull the trigger it's all business. Identify the animal, decide I'm going to shoot it, get setup, get a range if needed, bang.
Occasionally the opposite happens and I have all the time in the world. That is when it's really important for me to remind myself that I've shot thousands of rounds in my life, I am a good shot, I know what I need to do to get it done, and I can be excited when I'm standing by a dead animal because it's not done yet. Both my last elk and deer gave me probably 15-20 minutes of watching them, deciding whether or not they were a shooter, picking the spot or spots I potentially wanted to shoot them in and what my position might be for each shot, and waiting for them to walk to one of them.