This right here is about 99% of my irritability. My kids are just being kids, and after a long day of work (get up at 4AM), I just can't deal with their volume and energy when I get home. I do a good job of managing my irritability around them and never get aggressive or lose my temper.
The other 1% comes from terrible drivers, which is rampant where I'm from. I'm definitely ready to go apeshit when someone cuts me off and/or drives like a complete asshole.