There will be many situations in which you need to give feedback to others in the team. Like, they have just written a draft of a team paper, and you need to suggest changes and point out problems. When you give feedback it is extremely important to avoid any negative comment that would seem to be about the person, rather than the work or the behavior. You should also focus on yourself and your objection rather than on them and their problem. It is very important that teams assess their performance from time to time.
Most teams start out ok, and then drift away from their original goals and eventually fall apart.