What did MJ mean?

Well...

When u fall in love you get butterflies. That person is all you 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 or hurts you, it hurts your very and you cry

That's the difference :)

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