Does having a sudden mood change bad?

i was in school today like any other and for some reason i felt depressed or sad whatever it was it made me fel like crap. it made it worse when my friends started worrying about me i just didnt know. i wasnt thinking like how i used to and i wasnt in the mood to be sociable or happy in anyway my friends were really worried and i kept thinking im just bringing them down. does this suddenly happene through time to time i feel horrible feeling like this and i really want to get better is there anyway to feel better. this is driving me crazy i need answers badly.Does having a sudden mood change bad?
Lots of people have mood swings, but I think usually there's something that kicks them off. Some people also have mood disorders, and take medication. I would talk with a counelsor to see if you can figure out if something might be causing your mood swings, and if you may or may not benefit from some medicine.