I lost the very first deer I ever shot, and it made such an impression on me I have not lost another one yet, although I realize it is probably enevitable. I came close to losing another one early in my career, but found it halfway through thenext day, through sheer determination. I now approach tracking as a puzzle that can and must be solved,with all the information there if I can just find it and unravel the threads. Not just a physical but mental exercise. As Greg has stated, half the battle is proper mental attitude...
With that said, I think most people would be much better prepared if they thought much more about tracking their deer before they ever took the shot. I am thinking about tracking before the arrow ever leaves my bow. I mean, obviously not to the point it affects my shot concentration, but to the point my mind is prepared to absorb the rapid post shot evaluation of what is occuring in that compressed time frame when the deer runs off. Where it was standing, what my shot looked like, how the deer reacted, how did it travel, landmarks it passed and so on. I never can understand how some of those guys on T.V. spin around and start talking to the camera before the deer is even out of sight (but I digress...).
Give it a few minutes after the shot, then calmly get down and find your arrow for evaluation if possible, and sit on the ground with it for a good while, just thinking about all the information you have. Then and only then will you have what you need to determine your course of action from there on out. Unless of course your deer is dead within sight, in which case you should be taking pics to enter in the contest.
But seriously, I bet I would not be half the tracker I am now if I hadn't lost that very firstone. I have made many mistakes, but learned from every one.