I have come to realize that there are two kinds of criticism.
The first kind of criticism really is criticism. It is, to quote Webster's, "the act of expressing disapproval and of noting the problems or faults of a thing". It is the sort of thing just gets blurted out - sometimes casually, sometimes without thinking - or perhaps is the results of a carefully thought out meditation event.
In general, it hurts the person it is a directed at. And it scarcely accomplishes what it was intended to do.
It fails because it elicits two responses in the individual:
First, it almost immediately makes them defensive - after all, it at least feels like it is an attack, and if I am being attacked my first response is to defend myself against further attacks, not open myself up to listen more closely.
Second, it is almost never offered with a solution. It is a denoting that something is being done wrong or is wrong, perhaps with a sigh or a certain tone of voice. It is wrong because it is wrong (at least in the eyes of the critic). Implied, usually, "is stop it" - stop doing it, stop being it, just stop it.
The result is seldom what the critic imagines. They perhaps envision the individual hearing the criticism, gently considered it, and then saying "Yes, of course, I will stop it/stop doing it/stop being it". More often than not, the criticized react precisely the opposite way: made to feel small by what they feel is an attack, they either begrudgingly change their behavior or simply shut down. After all, if one cannot do anything right, why should one put in the effort?
The second kind is really more of correction than criticism. They both have the same origin - something is wrong or incorrect - but in the second version, a what and why is offered in the context of doing something better. And the thing hardly ever comes across as an attack - instead, it is an attempt to improve something or someone and make it or them better. One leaves the experience feeling better, not worse. (As a side note, usually this kind of correction is always accompanied by commentary such that the critic verbally reassures the one they are correcting it is not directed at them in a personal way, but rather for the purposes of making them better.)
Both may have the same initiating thought: something is wrong and needs to get fixed. But one truly has the concern of resolving the issues. The other seems more of an exercise to get the thing that is bothering them off their chest.
But one ultimately makes a difference and builds bridges. The other merely destroys them.