I heard this broadcast by Joni and Friends on FLR 90.3 the other day and was blessed and challenged to think of what my 'best thing' is and how to truly sacrifice.

A Costly Offering
This is Joni Eareckson Tada. If we're going to sacrifice something to the Lord, it has to cost us- that's the nature of a sacrifice.  A sacrifice to God could be our time or money, prayers, or talents. My friend, Carolyn, is a seamstress who barely makes ends meet by sewing for her clients. She lives alone and works late into the night, stitching up a storm. Last Christmas she wasn't able to buy the gifts she would've liked; so she went one better- she stayed up extra late, making presents of skirts and vests. Her friends were going to receive the best she could offer, even if it meant early hours and sore fingers. Friend, what is your "best thing"? No doubt it is something which has cost you. When we offer our best, it always takes a bite out of something we hold dear. So always offer to God your best. And when you do, you will be happy about it because it is a true gift of love.
~Joni Eareckson Tada on Joni and Friends