I almost stepped on one earlier and I legitimately freaked out. And I had to get someone to kill it for me. Not my proudest moment.
I've never been able to explain why I'm afraid of them so much though. One of my friends is fascinated by them while I can't look at them without getting shivers down my spine. I once found a spider in my room and, after it disappeared, made someone search for it for a solid 10 minutes while I waited outside. I can understand some other common fears like heights, but why do so many people fear spiders?