"...many of God’s people are constantly under apprehensions of calamities which will never occur to them, and they suffer far more in merely dreading them than they would have to endure if they actually came upon them. In their imagination, there are rivers in their way, and they are anxious to know how they shall wade through them, or swim across them. There are no such rivers in existence, but they are agitated and distressed about them. An old proverb says, “Don’t cross the bridge till you come to it;” but these timid people are continually crossing bridges that only exist in their foolish fancies. They stab themselves with imaginary daggers, they starve themselves in imaginary famines, and even bury themselves in imaginary graves. We are such strange creatures that we probably suffer more under blows which never fall upon us than we do under those which do actually come. The rod of God does not strike us as sharply as the rod of our own imagination does; our groundless fears are our chief tormentors, and when we are able to abolish our self-inflictions, all the worries of the world become light and easy. However, it is a pity that Christians who have the gift of faith in Christ given to them, should fall into so guilty and at the same time so painful a habit as this of fearing the oppressor who does not come, and who never will come."
~Needless Fears, sermon #3098 by Charles H. Spurgeon
Video for full sermon below. This quote above starts at 4:10.