As a kid, I was methodist. I knew an Anglican (Episcopal) nun a
   few towns away. She was very happy and social, working with the
   community. In my 20s, I had a data entry job at a Roman Catholic
   university and saw nuns, monks and priests there. The nuns there
   seemed very happy (as did the monks and priests). It made me
   realize it's a lifestyle I could do. Just after that, I
   converted to Eastern Orthodox. Spent a little time (not much) in
   a monastery. They were happy there, I enjoyed it. I knew I could
   do it. Monks are male and female in the Orthodox, "There is no
   male or female in Christ", although monasteries are nearly
   always gender separated for practical reasons. I'm not with them
   now. I've been agnostic for a long time but I enjoyed my
   experiences with them. So, my overall bias is that, yes, they
   seem to be generally happy.