Firm wrist for sure strokes
Firm strokes mean consistency. A key to firm strokes is a firm wrist. Loose, flippy swings may look graceful, but they tend to break down under pressure. The more moving parts you put in your strokes, the greater your chances of being erratic.
Play with a floppy hat but not a floppy wrist!
Watch a great shotmaker like Jimmy Connors. As the ball approaches, he locks his wrist -- and leaves it locked throughout the stroke. There's no slackness in his action.
If your wrist isn't firm, you have to rely on precise touch. When your touch is working, your game may be fine. When it isn't, though, you might just as well swing a fly swatter as a tennis racquet.