Innocent, Burned, and Courageous People

Humans start off with a mentality that can be considered as very "innocent." Over time, there's a very high chance that they'll experience the darker side of humanity, be it in the form of betrayal or something else such as murder. They'll then often turn into a much more cautious person as they've already been "burned" once. A significant portion of people stay at this burned phase as it is incredibly hard to move past it. At this stage you doubt almost everyone's intentions and will find it very difficult to trust others.

It takes an immense amount of courage to be able to open up your heart to another human after you've been hurt.

It's a horrendous thing for your mental health if you're never able to move past the burned phase. It's also very dangerous if you never left the innocent phase. The optimal stage is thus the one that shall be referred to as the "courageous" phase.