Here is a poem by Dietrich Bonhoeffer, written to his friend Bethge, while on his second trip to America. As you may detect here, he was overcome with doubts about whether he should be going or not.
The beginning and the end, O Lord, are thine; The span between, life, was mine. I wandered in the darkness and did not discover myself; With thee, O Lord, is clarity, and light is thy house. A short time only, and all is done; Then the whole struggle dies away to nothing. Then I will refresh myself by the waters of life, And will talk with Jesus for ever and ever.
From the book Bonhoeffer: Pastor, Martyr, Prophet, Spy.