Generally, I think I do a good job following these rules. However, you can't always be positive, IMHO. When there's something not working in a piece I think it's important to point it out. It can be challenging to express these issues in a sensitive and polite way. I do not always succeed in being sensitive and polite but I do always mean well. Mea culpa. I am working on this.
I sincerely want the author to write their best story and sell it!
On the other side of the coin, getting critique is rough. Often a writer's first novel is quite autobiographical but critique of writing is always just that, critique of writing--not critique of the author. I hate to say it but getting published is tough and most authors get many rejections before their successes. A thick skin is as important to an author as a word processor!
Do you have any tips for giving or getting critique?