"BEING CRITICAL IS EASY, AND OFFERING CRITICISM SEEMS EASIER STILL. Yet constructive criticism - - the more refined and effective brand of critical feedback - - is like an art when compared to Nagging, Nit-Picking and Negativity... Nothing makes most people bristle more quickly than Unfair, Unskillful, or Unsolicited criticism. Yet there are times when offering constructively critical feedback is essential to maintaining excellence and strong relationships.
DESTRUCTIVE CRITICISM IS INTENDED TO HARM SOMEONE, derogate and destroy someone’s creation, prestige, reputation and self-esteem on whatever level it might be. This may be done intentionally or out of sheer ignorance and foolishness. Hence the word destructive is used. In practical life destructive criticism may be disguised as constructive to be more painful while harming. Valid examination of intention of critic is when asked to prove, to help or to be somewhat useful at all. Often destructive criticism comes from persons who are envious, cruel and those who judges in fields which are not their own.
CONSTRUCTIVE CRITICISM IS A COMPASSIONATE ATTITUDE towards the person qualified for criticism. Having higher experience, gifts, respect, knowledge in specific field and being able to verbally convince at the same time, this person is intending to uplift the other person materially, morally, emotionally or spiritually. For high probability in succeeding his compassionate criticism the critic has to be in some kind of healthy personal relationship with the other one, which is normally a parent to child, friend to friend, teacher to student, spouse to spouse or any kind of recognized authority in specific field. Hence the word constructive is used so that something is created or visible outcome generated rather than the opposite. Participatory learning in pedagogy is based on these principles of constructive criticism. Here the saying applies that example is better than precept.
There can be tension between constructive and useful criticism; for instance, a critic might usefully help an individual artist to recognize what is poor or slapdash in their body of work—but the critic may have to appear harsh and judgmental in order to state this. But useful criticism is a practical part of constructive criticism."
HOW TO GIVE AND RECEIVE CRITICISM: http://www.scottberkun.com/essays/35-how-to-give-and-receive-criticism/