Once again, thanks to the January 2011 issue of Real Simple for this thought-provoking question. The answer: Safer Than a Known Way by Pamela Rosewell Moore. This missionary's autobiography is an amazing story of how she set stipulations for serving God and willingly followed as He changed her expectations one-by-one and lead her into the unknown. The title of the book is from a poem that has become an ongoing reminder for me to put my trust in God through all my own life's unknowns.
"I said to the man who stood at the gate of the year: 'Give me a light that I may tread safely into the unknown.' And he replied: 'Go out into the darkness and put your hand into the hand of God. That shall be to you better than light and safer than a known way.'" -M.L. Haskins