Play the numbers
I do this practice drill when my rhythm is off, but it's equally useful to groove distance control. I drop nine practice balls on the ground and, using my 7-iron, start by hitting three balls softly. They go about 148 yards. Next, I hit three more balls, this time with medium speed, and figure them for 155 yards. Finally, I hit three balls as hard as I can (without losing my balance). By now I'm up to 162 yards. Try it. You'll learn that an easy 7-iron goes as far as a hard 8. Sometimes conditions like wind or elevation change favor one over the other.