How is Friar Laurence's decision to leave the tomb without Juliet an emotional decision?

When Friar Laurence comes into the cemetery in Act V, Scene 3, he is immediately worried because he meets Balthasar, Romeo's servant, and sees a light at Capulet's tomb. He knows that Romeo never received the message about the plot to fake Juliet's death. He says,

O, much I fear some ill unthrifty thing.

The Friar is obviously afraid of what Romeo may be doing and his fears are recognized when he sees blood stains on the opening to the tomb. By the time he gets inside he finds Romeo dead and Juliet just waking up. A number of emotions must have passed through his mind, including regret, anxiety and fear for his own life. He reveals this emotional side when he hurriedly leaves the tomb without taking Juliet. He believes his plans have been ruined by some higher power. He says,

I hear some noise.—Lady, come from that nest
Of death, contagion, and unnatural sleep.
A greater power than we can contradict
Hath thwarted our intents. Come, come away.
Thy husband in thy bosom there lies dead,
And Paris, too. Come, I’ll dispose of thee
Among a sisterhood of holy nuns.
Stay not to question, for the watch is coming.
Come, go, good Juliet. I dare no longer stay.

This sudden display of emotion seems to go against Shakespeare's earlier characterization of the Friar as calm and logical, with an answer to every problem that arises for Romeo and Juliet. He wisely tells them to take things slowly when he marries them, and when Juliet finds herself facing a marriage to Paris, he again has a reasoned (though desperate) solution. That he should show such raw emotion at the end of the play and flee for his life is out of touch with his earlier actions. As with the character of Lord Capulet, who uncharacteristically changes his mind about Paris and then berates Juliet, Shakespeare apparently needed Laurence and Capulet to reveal their emotional sides in order to move the plot to its tragic ending.