Why do I feel so many emotions at once?

today, seem like it was going well until my order got cancelled. I got made cause they could of just called and said we don't have this, wanna get something else. but my brain got angry. from angry, I felt useless, from useless I remember how many times I messed up on things. my boyfriend try to calm me down. I thought it's just not working and making money, I feel useless, no good. as of people have to take care of me for the rest of my life. I've been doing this alot tho, get mad, feel sad, than depressed. I don't know why, can someone tell me why I'm going through all these emotions at once?