Do you think being too chronically happy could be a mental illness the same way that depression is?

Well that depends..... if someone who's "chronically happy" is laughing and still being their happy self during a horrific time ala 9/11, yes that IS a mental illness in the same way that depression is a mental illness.
Which is much different than positive happy people.... who SEE a glass that is half way filled as being a half FILLED glass, whereas the negative minded people SEE the same half glass as being half EMPTY.