“One of the difficulties in mending for most anglers is that their technique eliminates slack in the line and leader, rather than creating slack or moving it to a new position. If the angler starts with no slack, and starts yanking on the line at the rod tip, the fly will move. At worst, the mend will negate casting accuracy by pulling the fly out of the fish’s feeding lane or cause enough drag to spook the target fish. “Mending Your Ways” by Brant Oswald
Middle Fork Willy: To mend now will move the fly as it moves along that far seam. An earlier, bigger mend would have kept the fly in the zone longer. The fish were rising along a 10′ stretch of the seam. I was maybe presenting to half that distance without drag ensuing. Notice the competing current speeds on the fly line. (SwittersB)
Oswald writes a nice beginner’s tutorial (intermediate’s reminder) on mending the fly line. The effort is to develop a balance in feeding line up trough the guides and/or adjusting the speed of the fly, via mends, without disturbing the fly and alarming the fish. The correct tension upon the fly line that maintains natural speed (moving at the speed of the current, not speeding up because of drag on the flyline/fly) is a skill that is much more important than how long a cast you can make. It is an important act that is often performed too hard.
“Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be
satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience.”