This happens to me almost every night.
I'll be peacefully laying on my bed with my eyes closed until my mind suddenly gets bombarded with all these random thoughts and I try to blank everything out but they just keep coming and coming and coming... Most of those thoughts are provoked by my worrying about certain things that are to come the next day like "Tomorrow's gonna suck", "I'm going to fail that test", or "I'm going to make an ass out of myself during tomorrow's presentation" and other negative stuff like that.
I know I'm doing this to myself by being so negative but I really don't know how to control those negative thoughts and they always end up poisoning my mind and soul.