Give an example of constructive criticism.

If someones playing the guitar and its good but the persons strumming or hand positioning could be better, telling them how to improve those things would be considered constructive criticism.

An example of constructive criticism is: "I noticed that we have had some trouble communicating lately. What can we do to improve this?" An example of unconstructive criticism is: "You haven't been communicating with me lately. What's your problem?"