Feeling Good One Moment, Then Everything Crashes Down

There are times when I'm feeling good and then all of a sudden it's like a dark cloud just forms over my head and everything comes crashing down. I feel an overwhelming sense of sorrow that is often accompanied by anxiety, paranoia, guilt, and sometimes even physical symtoms such as a headache and a sick feeling in my stomach. Does this happen to anybody else, and if so are they any ways you've learned to cope when this happens? I know I kinda suck at explaining things but these moments happen randomly with seemingly no trigger so any feedback you may have is appreciated. Thanks.