I'm going to talk to you about the width of your cross-court shots.
The standard place to aim is just behind the back of the service box, here on this amber target, catching the side wall before it hits the floor. The reason we aim here is to get it past our opponent on the 'T'.
That is assuming that our opponent is in the normal position on the 'T'! This is where you need to think what you are doing when you are on court. You can't just hit standard shots. You need to adapt your shot to the situation.
Lets say you are playing someone who has you in a bit of trouble at the front and they are a really good volleyer. They are going to push forward on the 'T' so you will need to aim a little bit wider...perhaps this red target here.
If you hit here with your opponent forward on the 'T' they are not going to able to cut across and volley it...and if they step forward it is going to cause them problems. If you hit the amber target, the one you usually hit, they will be able to cut that out.
If we find ourselves in a great position..lets say you have played a good ball into the front forehand corner and you opponent is stuck and they are not on the 'T' there is absolutely no need to hit wide onto the side-wall here.
If you hit onto the side wall the ball is going to come back out and will give your opponent a good chance to hit the ball. If we aim somewhere for the green mat here..the ball is now going to be taken away and die in the back corner.
The key though is that our opponent is not on the 'T' so we are allowed to aim for the green mat. If your opponent is on the 'T' and you try and hit here they will just cut it out.