What Exactly Means To Be "positive"?

What Exactly Means To Be "positive"?

A sister in Relief Society mentioned today about the importance of being "positive". Our branch right now is struggling with people who went less active because somebody has "offended" them so this sister was stating this as an example. She was saying that (because of this type of situation) we need to remember that what we say can destroy the lives of other people and because of it, we need to always talk positive things to others and not negative things.

My questions are:

1. What exactly mean to be "positive"?

2. What is the difference between being positive and being optimistic?

3. Does this mean you cannot talk with a brother or sister and point a problem because it is not "positive"?

4. How "positive" are you in your interactions with members?