Appreciating and complimenting your partners strengths is a sure way to help their confidence and make them play better!
We all love to feel like we are playing well and that our partner is pleased with our performance!
As an example - often at my level - people who hit very hard also miss a lot of shots. They hit out and are less consistent. However - their ball is also really hard to poach or to smash!
So instead of getting annoyed at the balls in the net or that hit the back fence - I focus on the fact that my partner scared the opponents with her pace!!! If you want to win more - and have more fun - then FOCUS ON YOURS PARTNERS STRENGTHS!