Kids & fighting

Why? Why must children fight over the most insignificant things ever? Today Jakob & Jackson were fighting over could open the front door. Really? Come on. There are some days where I think my head might just explode off my body. I don't understand it. It's days like these where the fighting starts the minute they all 3 get in the car together & I question what I was ever thinking. What was I thinking? Was I thinking , oh, I want 3 amazing kids that get along and have the perfect little family, or was I thinking I want 3 kids that drive me totally insane. There are days I honestly question my sanity & my job as a mother. OK , I'm sane just for the record but there are times I question it. Sometime I wonder if I'll be in the nut house before all my kids are grown. Maybe? I hope not, but we'll see.