Look, please don't take this as an attack or something like that against Orthodoxy, because it is not, but I'm just speaking generally, if I see a nun or a monk who is supposed to be very close to God and gave up his/her life to the Lord and then I look at them and see them look miserable, not smiling, I would wonder what on earth is going on that makes them look sad. Jesus Christ came to earth to give us life and to have a better one, not to look sad as if God is always angry at us and we need to act like we are in funeral, that is far away from Christianity, and the God I know is not scary and unforgivable God.
And what do you think non-Christians would think when they see a nun who is supposed to be close to God looks sad, I'm sure they would stay away from whatever religion she follows.