This is a Ceasar Cipher in which each letter of the alphabet is substituted for a letter at a fixed number of positions down the alphabet.

Therefore, if ‘b’ becomes ‘x’, the other letters shift accordingly.

Juliets diary entry reads:

‘Alas, I am past hope, past cure, past help.

I long to die.

I must go to the cell of Friar Lawrence for counsel.’

The answer is: CELL OF FRIAR LAWRENCE