Let us praise the slightest improvement that inspires the other person to keep on moving and improving. Psychologist Jess lair comments: “Praise is like sunlight to the warm human spirit; we cannot flower and grow without it. And yet, most of us are only too ready to apply others the cold wind of criticism, we are somehow reluctant to give warm sunshine of praise.
What matters is not what I think of him/her, but what they think of themselves
In short, if you want to improve a person in a certain aspect, act as though that particular trait is already one of his/her outstanding characteristics.