Even though they both sort of mean the same thing, when you think of yolo, you think "you only live once" which means to "live life to the fullest" but a lot of dumb asses think that phrase means "be stupid and do stupid things because you never know if you will wake up tomorrow so what the heck?" Even though it isn't its true meaning. While with Hackuna Matata, people just think about the amazing movie it's from, and it's meaning. "It means no worries, for the rest of your days...." But like I said, although they both mean the same thing pretty much, when you hear about what many idiots in this world have done, you never hear, "Because Hakuna Matata" but instead "Because yolo", therefore yolo is viewed by a lot of people as bad even though it's not, but people don't seem to understand its true meaning and the concept that's its trying to put out.
Also carpe diem should be an option