Smiley,
Like you, I take a lot of lessons. I worked very hard last summer and improved many things about my form. By the fall, I was ready to start *spanking* people by spanking the ball.
In September, the combo season started. And suddenly I couldn't hit the shots I wanted. My form looked better and was better, but still I missed. I would lose to players who had inferior technique.
After taking one particularly unfortunate beating, I talked to my pro about it. The advice was that I had misunderstood the purpose of good form/technique. The point of good technique is to achieve consistency. If you set up correctly and swing low to high while you keep your eye on the ball, you pretty much cannot miss.
Regarding power, much of it comes from good technique. At the same time, it is a mistake to go for power for power's sake. It's like the accelerator of a car. You only push the accelerator as hard as you need to. No need to stomp on it. Same thing in tennis: use power for a purpose, and don't stomp on it for no reason lest you waste gas or lose control.
I took this advice to heart, and suddenly I started doing much better. I was letting the technique do the work rather than trying to stomp the accelerator just because I had paid big bucks to learn how.