Taken from the fourth opening (or third, if you dont wanna consider the edm version of the first opening, an opening) of the JoJo's Bizzare Adventure Part 4: Diamond is Unbreakable anime, it is a term used to specifically describe a JoJo fan's mental or emotional breakdown.
Holmes: "Yo, you heard what happened to that JoJo fan from our class yesterday?"
Jake: "Yeah, looks like his crush rejected him. After that he had a severe BREAKDOWN BREAKDOWN."
Breakdown breakdown is a sentence of the JoJo's Bizarre Adventure part 4 opening "great days", right when this song starts the singers yells BREAKDOWN BREAKDOWN, causing it to become a meme of it's own by using it out of context by saying you're having a blank BREAKDOWN BREAKDOWN , this meme is commonly used by JoJo fans
-random guy: "Hey dude how are you"
-you: I'm having a mental BREAKDOWN BREAKDOWN