Most golfers hate partial wedge shots because they don't have a good plan for playing them. They tend to make too big a backswing and then have to decel at impact to avoid smashing the ball over the green. When you slow down like that, everything gets out of sync, which makes it tough to catch the ball solid.
The secret to these shots is making a shorter, wider backswing (above, left), so you can accelerate through the ball. You want to be able to rotate your torso and swing your arms faster on the downswing—that's an athletic move that produces more consistent results. When everything moves through the shot together, you can make a firm strike and not worry about putting too much on it.
I tell my students who struggle with these shots to commit to this phrase: "Wide back, accelerate through." Get your body facing the target at the finish and your arms farther through than they went back (above, right). To do that with confidence, the key is a shorter backswing.
When you have to hit a wedge shot high, I bet you hang on your back foot and try to help the ball up—catching it fat or thin. You need to get your weight forward as you swing through. Start with more weight on your front foot. Then swing back, and shift to the target coming down. At the finish, check that you're using your back foot only as a balance point.