There's a moment in tennis that deserves your complete attention.
It's a long moment but it can feel short. It starts when your opponent begins his tossing motion, and it ends when the ball is in front of you; in between you must be alert and responsive.
As he begins the toss, get your feet forward onto the balls of your feet, so you can respond to the serve with your feet. Hold your racquet in front of you, in case the ball comes fast and there's no time to do anything but block it back.
Just before he strikes the ball, open your eyes wide and take note of the position of the toss; it may give you an indication where the serve is headed.
After the ball is struck, intensify your movement; get the racquet back fast, move your feet and importantly, keep your eye on the ball.
When the ball bounces, intensify your concentration; follow it as long as you can. Then hit it.
Matches are won and lost on the consistency of hitting serve returns. The ball lands in the middle of the court. With nothing on it. A grapefruit. It could just as well be sitting on batting tee. You miss it. You miss it because the last thing you say to yourself is, "Don't miss it." Not good.
Any sitter, and especially a fat second serve, deserves respect. Intensity must be raised. And the approach taken must be positive. Instead of thinking, "Don't miss", think "MAKE".
Hit the ball on a line. Think aggressive and solid. Think forward. Think step into the ball, head down. Think crosscourt, down-the-line or down the middle -- whatever -- but have an idea.