(dumb) need to vent, any advice

I was at a fast food place and waited 20 mins for my food they totally skipped me so I told the manager and I got my food, I took a bite and it was nasty 
Now remind you I was already beyond pissed and hungry and annoyed so I got up to leave and knocked down a stick of those little cups you use to but ketchup in and some workers saw me 
I feel bad now but I was mad and for some reason lost my cool can you help me feel better