1. When the person behind you leaves four seconds after you instead of five.
2. Or even worse, if they leave three seconds behind you.
3. When the person in the lane next to you leaves early.
4. When there's a set on a weird interval like :25 or :35, so you have to do a lot of complicated math in your head.
5. When someone in your lane sprints the warm up.
6. When you hit your hand on someone in the lane next to you.
7. When you get stuck in a wall lane for practice.