Its really easy to criticise, either yourself or other people, but the truth is it rarely, if ever, does any good. What happens when you criticise someone is it sets up their defenses and instead of looking rationally at situation they go into survival mode and try to defend it.
There really is no such thing as constructive criticism because from the moment you go into defensive mode you’re working from your reptilian brain which only deals in black and white. In that state something is either all wrong or all right, so even mild criticism is taken to the extreme and sets up a person’s defense mechanisms. Its really difficult to get any kind of improvement from the reptilian state because, remember, the reptile hates change and will resist any attempts to make it “better”. And at the reptilian level our intelligence is a fraction of normal, so logic is way out of our reach. You really can’t reason with an iguana!
People who tell you they are criticising you “for your own good” are really not helping, even if their intentions are good. The best way to get improvement is to tell someone what they are doing right, not what they are doing wrong – remember, what you focus on is what grows. If you constantly focus on what is right you allow their confidence to grow to the point where there is no space for the negative. Most of the time people know exactly what they’re doing wrong and given enough confidence they will tell you themselves, and ask for help to improve. This comes from the “human” brain, where change is welcomed and embraced rather than resisted.
Even when someone asks you to critcise them, the best way to get results is to focus on the positive – tell them what you see them doing well, then ask them what they would like to do better. Making someone feel positive about themselves will alway bring about a willingness to change and improve.