I had a really bad toothache once. It took several days for the dentist to be able to see me, and I hardly slept the whole time. I was lucky if I could get a couple of hours of (broken up) sleep per day. I'm pretty sure that's the only time in my adult life that I've cried from pain. All of this happened around my birthday. This was also when Miitopia came out, so now whenever I'm not feeling great I get the urge to play that game.
Second place would be the first time I dealt with costochondritis (inflammation of the cartilage around rib cage). If it had been on my left side, I would've been 100% sure I was having a heart attack. The pain got so bad that at one point I had to lie perfectly still in a weird, very specific position in order to make the pain bearable. I've dealt with it a few times since then, but none of it was as bad as that first night.
Second place would be the first time I dealt with costochondritis (inflammation of the cartilage around rib cage). If it had been on my left side, I would've been 100% sure I was having a heart attack. The pain got so bad that at one point I had to lie perfectly still in a weird, very specific position in order to make the pain bearable. I've dealt with it a few times since then, but none of it was as bad as that first night.