"There are plenty of people who are ready to talk about, and even attempt to perform some "big thing," some huge, glorious, magnificent enterprise (or ministry), but when they come right down to the small and practical details of the undertaking, they are disgusted with everything that looks like details, and so they turn away." 
God usually prepares us for ministry by working in lowly positions first, and usually in another's vineyard to see if we will be faithful in small things.