According to the internet, the Friar is referring to Juliet's parent that them crying is normal and natural, but since Juliet is in a better place, they should rejoice for the dead and that her soul is still pure when she goes up to heaven because she is young.
Or,
Natures tear meaning natural tears, merriment meaning happy. It is natural to cry over the death of a child but they should be happy she is going to be in a better place.
The passage above is an excerpt from this. If the underlined word, which is "crisis", be substituted with the word "event" instead, this would create a tone of less intense. Answer is opt
