Physical Danger
Cloistered behind the monastery or abbey walls, you can rest pretty easy. You won't be dodging bullets or operating heavy machinery anytime soon.
You should give some thought to the toll that such a solitary and routine existence will have on your health, though. You're going to have a lot of time alone with you, yourself, and...you, which can really bum you out after a while. Make sure you get out into the fresh air every once in a while.
If you can keep yourself together mentally, you'll be in really good shape. The life of a nun or a monk is no different from any other person, though they have low rates of various cancers compared to the rest of the population.
Trading a large paycheck for a longer, healthier life sounds good to us.