What did MJ mean?

Well...

When u fall in 爱情 你 get butterflies. That person is all 你 think about. It's like being HIGH. it's the most wonderful feeling (like a high)

However... When you're in love, and that loved one theta hurt 或者 hurts you, it hurts your very and 你 cry

That's the difference :)

i would say 'falling in love' is the start...u start falling in 爱情 and then 你 are in 爱情 and thats 'being in love'
maybe he means it makes him high to fall in 爱情 but when he is in 爱情 he cries? IDK! hahaha its just a song 'high' and 'cry' rhyme ...