Hey, I'm in the same position you are and I don't have any special insight into this, but I think it varies so much that you won't really get a good answer. The numbers above are reassuring, I guess, but there are just too many variables. Some variables I can think of are:
-How good of an interviewer you are and your social skills
-The quality or desirability of the program itself -- my guess is that if your top 4 are all highly competitive and desirable programs it will make it harder to match there. Conversely, might be easier to hit your #1 if it is a smaller, less known program
-The number of interview invites a program grants -- a program that interviews a ton of people might make it harder for you to get your #1 choice
-Specific program directives -- are they looking for a 'diverse' class, lots of phds, geographic variability
I think the biggest factors is probably #1 and thankfully the one you could have controlled the most. I know its really stressful, but there's nothing we can do about it anymore. Speaking personally, my top 4 seem to be liked by many other people on the interview trail, so I'm not holding my breath and would be really surprised if I matched in my top 4
As for the stress, I'm trying to remember why I wanted to be a pediatrician in the first place (remember, its not about where you train, but what kind of doctor you are). this is not working so I'm drinking a lot of beer, watching netflix, spending way too much time on sdn, and drinking more beer.