What did MJ mean?

Well...

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

That's the difference :)

i would say 'falling in love' is the start...u start falling in love and then آپ 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 ...