From the wikipeda article about Criticism.
Criticism as an evaluative or corrective exercise can occur in any area of human life. To criticize does not necessarily imply "to find fault", but the word is often taken to mean the simple expression of an objection against prejudice, or a disapproval of something
With criticism it is always important to keep things in proportion, neither overdoing things, nor being too timid.
People can be too critical, but they can also be insufficiently critical. It is important to strike a good balance: to be neither excessively critical nor completely uncritical.
People who are too critical and focus only on the downside or limitation of things run into the problem that others perceive them as being "too negative", and lacking a "constructive attitude". If there is too much criticism, it gets in the way of getting anything done - people are just "anti", but "it does not lead anywhere".
People who are uncritical, however, are often regarded as naive and superficial ("suckers"); they lack discernment, they are prone to being deceived and tricked, because they readily believe all kinds of things, which they should not accept just like that, for their own good. If they thought more critically, they would not give in so easily to what others say or do. The idea here is that "one should not be so open-minded that one's brains fall out."
Positive and negative effects
People can also be hurt by criticisms, when they experience the criticism as a personal attack. Psychologists concerned with human communication, such as therapists, therefore often recommend that people should choose the right words to express their criticism. The same criticism can be raised in different ways, some more successful than others.
timely, not too early nor too late.
brief and succinct, with a clear start and a finish, not endless.
relevant and to the point, not misplaced.
clear, specific and precise, not vague.
well-researched, not based on hear-say or speculative thought.
sincere and positively intended, not malicious.
articulate, persuasive and actionable, so that the recipient can both understand the criticism and be motivated to act on the message
Criticism is made at the wrong time and place: people might accept that the critic has a point, but "they can't do anything about it now."
Criticism is too long: people get confused over what it is all about, they get lost in it, and become disoriented.
Criticism is vague: people are likely to say, "so what"?
Criticism is inappropriate, or the critic is not really in a position to make it: people will say "you're way out of line".
Criticism has no clear target: people are likely just to conclude that "so-and-so is in a bad mood right now" or "he's had too much of it."
Criticism assigns blame or states problems without suggesting solutions: people are likely to conclude this information is not very useful.
Critic did no research before making the criticism: people will say, "very interesting, but this cuts no ice."
Criticism has no clear motivation: "why are you telling me this, and why are you telling me about it now?".
Critic makes bad criticisms regularly: it discredits the critic.
It’s a reason why I bold and italicize some parts....
