Everyone needs to be valued and it is a tremendous chesed (kindness) to express appreciation to others. Hard work becomes much easier when you are appreciated for your efforts. Unfortunately, many people find it easier to criticize and complain than to express gratitude or admiration. A person who utilizes his power of speech to enhance the lives of others will not use this power for destructive purposes. Moreover, if a person has pained others with words in the past, he shouldn't make up for it by presently doing many verbal acts of chesed (kindness).
From the Power of Words by Rabbi Zelig Pliskin 1988 p. 35-36
Write short notes of appresiation to as many people as possible as often as you can. Think about the people you take for granted. What notes of appreciation can you write to them? When specifically will you do this?
Very often people fail to express their appreciation to others because they assume that those people realize they are appreciated. But in reality this is not always the case. Often, if you do not express your positive feelings towards someone and his behavior, he will not be aware of your true feelings. It is tragic how frequently appreciation is not acknowledged although it exists. Always assume that you need to tell someone of your appreciation for him. Nothing is too insignificant for you to express your appreciation about, and the other person sill always be grateful for your thoughtfulness in expressing how you feel about him.