The other end of the spectrum from "taking life seriously" is:
life as play; life is important but important doesn't mean one can't play
life is frivolous; nothing is important
other; fill in below or comment
Other? (or other text as is appropriate/inappropriate)
Being called frivolous really did surprise me. Silly and Play I can understand but lacking in goals and accepting any choice being no more important than another because life isn't "serious" just seems weird to me.