Due to my mother's health (My Niece Died This Morning) and their relative poverty, my parents assumed they would never be able to serve a "regular" mission as a couple. However, after talking with their bishop extensively they decided that they would be able to serve at Cove Fort (an historical site not far from their home), since it would not be stressful on my mother and would cost very little. They planned everything accordingly, submitted their papers with that specified by themselves and their bishop (with an explanation about why a regular mission would be impossible) and waited for confirmation of those plans.
They were called on an active proselyting mission to South Carolina - at the full cost for such a mission.
They had no idea how they would be able to do it - both in light of my mother's condition and their finances (they literally didn't have enough money to do it), but they accepted the call, attended the required training and left Utah to drive to South Carolina - not knowing beforehand what they would do.
It was a five-day drive for them. Three days into their journey, an elderly sister called their new Mission President and told him that she had received a strong impression that she was to offer the use of her small house to the mission - to be used for any couple who needed to serve in that area, totally free of charge. She would live with her son and daughter-in-law for as long as the mission needed her home.
The Mission President was unaware of my parents' dilemma, but he immediately felt impressed to have my parents live in that house and serve in that area. They did so for 10 of the 18 months they served - building lasting friendships and having a wonderful experience, and seeing their meager savings extend almost to the penny for what they needed for that mission.
God's hand operates all around us - not always in such visible and undeniable ways as my parents' mission, but powerfully nonetheless. The thing that strikes me most deeply about my parents' experience is that they had no idea how they would be able to do what they had been called to do. It literally was impossible without the direct and active participation of the Lord, but it took them stepping out into the darkness and committing to do something they knew they couldn't do for it to happen.
There is a valuable lesson in there, I believe.