My immediate family is small - two parents and a brother, and my extended family is not much bigger - a handful of cousins and aunts/uncles. Of those cousins one has severe mental health problems; it's not uncommon for said problems to seep into my day to day life. For many reasons I can't speak much about the problems specifically but they left scars on my upbringing/childhood – here's what I learnt about society at large as a result.
I believe that that the world is going through somewhat of a mental health crisis so this form of thinking may help others as well.
Power and control
Learning to deal with techniques like manipulation, abuse, and violence (including violent thinking), and more generally learning to realize and avoid fear when possible.
Unpredictability and ambiguity
Understanding how to incorporate resilience, flexibility, and commitment into planning, preparation, and thought in general, and learning to deal with adversity in many ways.
Focus and attention
Learning the importance of training focus, understanding direction, and only paying attention to what's necessary at all times.
Detachment
Understanding the qualms of attachment and learning to disconnect when necessary irregardless of the environment or situation at hand.
Mental health
Amongst others, learning issues like anxiety, depression, dissociation, and trauma, and how they pertain to the mind, and specifically how to notice and remedy them as early as possible.