What's the Difference Between Being Nice and Just Keeping My Mouth Shut?

False "being nice" means unconscious behavior that keeps us stuck in avoidance of how we feel, how it is for now and what is really going on.

True "being nice" flows - it's a natural behavior that doesn't require much thought. When we feel safe and no longer need other people to feed our need, we are genuinely nice.
Keeping our mouths shut can be the conscious decision to see things another way - to define the situation so we decide to forgive the other for their unconscious behavior or perhaps we put our inner reality on the shelf at the time and then take time when we are alone to see what bothers us about the situation and how the situation might serve us.

Keeping our mouths shut can also be avoidance. If we keep out mouths shut and work through our issues about the circumstance, we are freed, but if we keep our mouths shut and never deal with the issue, we add to the numbness of our souls.

If keeping our mouths shut helps us not to blame others or take their inventory, it's a good thing.

If keeping our mouths shut means not to yell and scream at someone, it’s a good thing.

It is our responsibility in our healing process to find a compassionate way to express our feelings. Giving unsolicited feedback to others is usually not a good idea. Most people complain so they can work through their feelings. The solutions they seek are on a feeling basis not an action basis. All these ideas are slippery because each action and behavior has a light and shadow side. It takes consciousness, compassion and awareness to determine which action to take.

I think the topic could be a book something like: "What I Thought and Didn't say Keeps me in Perpetual Trouble."