This weekend, I lost 115 rating in Codeforces Global Round 9, ranking 3024 and only solving problems A, B, and D (and not quickly). However, only a day after the contest, I have already upsolved C, E, G, and even H (unfortunately, not F), without much outside help.
The main reason I failed so badly was because after solving B (deciding to skip A), I got stuck on C. After making a WA submission, I started to panic, severely affecting my performance. I was freaking out, and started to try more approaches (3 more, in fact), all of which also got WA, contributing further to my panic. After a while, I decided to go back to A, and solved it (through I made it too complicated and took too much time, for someone at my skill level). I was also simultaneously working on D (often switching back and forth between C and D), and I was also stuck for quite a while.
I ended up solving D, but again taking way more time than I should due to my emotional state. By the time this happened, there were around 50 minutes left. I then started working on E (sometimes switching to C), but could not solve either of them during the contest. I looked at some other problems briefly, but did not seriously think about them due to my assumption that they will be too hard (which turned out to be false, especially with G).
After the contest, it turned out that I read problem C incorrectly (missing the fact that the two chosen elements must be consecutive). I did not look at the statement carefully during the contest, again because of the panic.
As I calmed down, I upsolved many problems from the contest.
A day later, I competed in AtCoder Beginner Contest 173, which is supposed to be easy for me. However, I ended up solving only 4 out of 6. The reason was similar; getting stuck on an easy problem, causing a panic which I did not recover from. After solving A-D, I wrote a lengthy solution to E using logarithms which got WA on a single test case due to precision issues (turns out, the code gets AC when double is changed to long double). I started to panic again, and tried approaches that do not use floating point, but taking way more time than I should. The new code was messy (because I was only trying to complete it as quickly as I could), and it keeps getting WA. I was not able to get it working before the contest ended. I opened F but did not think about it much, because I was focusing completely on E at the time (F turned out to be quite easy).
Does anyone have tips on staying calm when things do not go well during a contest (in other words, when one is unable to solve an easy problem)? Currently, for me, this is the main cause of large rating drops.