Why do people have to yell at people for no reason?

I have one person ignoring me and another one yelling at me for spending and using too much money but I spend $600 a month for food which is pretty average amount plus its my damn mlney? My dad left a little so i can be comforable and be able to get my education so i can get a job. And I NEED TO FEED MY FAMILY. But i got yelled at for buying a box of brownies. I hate this so much.