We reduce people around us. How often do we forget all the good things about someone and focus on their "faults" at worst or few "positive" things at best? When we forget to acknowledge good things about other people we create problems for ourselves and other people.
What kind of problems, you ask?
When you tell someone for long period (your child, your friend, your partner) that they are good at this one thing they might start to doubt their wholeness - they might doubt that they have other "good" traits or even doubt that they are able to have them in the future.
When parents tell to their kid that she is good at e.g. "math" it will be engraved in the child's mind. The kid might never have courage or desire to approach art, or literature, or sport.
If you tell someone they are "this", that also might mean to them that they are not "that" and can never be anything except "this".
So such reduction, affects your perception of another person, it might affect self-perception of that person, and it will damage your relationships too. If you tell another person that she is "serious," you deny the existence of "funny" side. In such case, that person might never be "funny" with you.
In theory, we are all independent adult creatures, in practice, it is not like that at all. Let's be careful with each other. Let's try to not project our insecurities on other people. Let's be explicit about all (even tiny) things we appreciate in each other. And also let's be conscious and mindful of those good things.
Maybe our kind words can change someone's life. Maybe we will bring a smile on someone face, or a tear of sadness followed by a tear of relief and happiness. Perhaps we will lift someone out of depression or difficult stage of life.
Let's not make assumptions about other people. Let's not think that our compliment will have no negative side-effects even if we said it with good intentions. Let's be kind and gentle with each other. And let's be attentive. Let's acknowledge each other wholeness.