Participating in a big competition like IOI or ICPC can be intimidating, the worst thing that might happen to you is that you manage to get nervous enough to enter that adrenaline-fueled fight or flight state, you start feeling that you need to get out of the contest fast. An easy bruteforce solution that would take you 2 minutes to code in a normal environment suddenly requires 10 minutes, or at least that's what happened to me the last 3 major competitions I participated in (APIO 2014, IOI 2014 and APIO 2015), while it wasn't very noticeable in APIO 2014 -I quickly forgot about it because it was my first medal a bronze one- and I blamed that state on sickness in IOI 2014, after APIO 2015 it became clear to me that I'm making the mistakes over and over.
If you're really new to competitive programming, someone who doesn't really care much about the result, or someone who's trained since the age of 6 you probably won't relate to these issues, but after I've done some research I realized that this is more common than I expected. The same pattern happened to me every time: I had the right ideas, I got WA on my first submission, I panicked and then my brain basically stopped working (and of course all the known symptoms of the fight or flight state).
I remember talking to someone after day 2 in IOI 2014, he told me: "When I read the problems, my brain stopped working I didn't even understand them, after the contest I read them again and came up with 243 points worth solutions". And his solutions were very neat and differ to the tutorials that were given to us after the contest.
So the point that I'm trying to make is: If I and everybody who suffers from the same problem, could solve problems during a competition as big as IOI with the same level of problem solving skill we usually demonstrate in any other environment, our results would differ greatly.
Have you ever had those issues? Did you manage to fix them?
Also in case of IOI-like competitions, what is your general strategy?
UPD: I got a bronze medal in IOI, the advice bellow is really helpful