4 Year Old

So, our 4-year-old is typically a happy child who loves to dote on people and help out where needed. However, when she gets really upset about something (ie. not wanting to wash her hand when you ask her to, or not getting a toy she wants to play with, or even hurting her knee when she falls etc) she will resort to the extreme response of saying things like: "I never want to go swimming anymore;" "I don't like this world;" "this task is too big for me, I'll just sit here alone;" "Well, I never want to come back here again." etc. Sometimes her tone is whiny and other times she's screaming while saying these things. Would love to know your thoughts on who to help her; how can we help her calm down, feel loved, and provide better confidence in her so she doesn't automatically resort to the big negative thoughts?