Rowan took the letter without hesitation. He sealed it in a leather pouch strapped over his heart. He landed in the dark of night off the coast of Cuba and make his way to the mountains, and after much difficulty, found Garcia. He handed him the letter, turned around and headed home. Hubbard tells this story in "A Letter to Garcia." Rowan didn't ask, "Exactly where is he?" or "I doubt if I can do it." There was a job to be done and he did it.
Instead of making a dozen excuses why you can't complete the task, think about Rowan. Deliver the goods!