Who said "I must not think too much of this, or I shall go mad."?

This quote is attributed to Jonathan Harker.

I must not think too much of this, or I shall go mad. - Jonathan Harker

"I must not think too much of this, or I shall go mad."

Jonathan Harker Fear

Character in Dracula

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"We must be united, or the enemy will exploit us."

"Time is the greatest enemy in our struggle."

"Love demands sacrifice, and sacrifice demands courage."

"We are all changed by what we have witnessed."

"Face your fears with courage."

"You can't live your life in fear."

"Snakes. Why'd it have to be snakes?"

"Fear is just another obstacle to overcome."