Fuerte en la cabeza means strong in the head, mental toughness. Mental toughness is many things, including the ability to stay cool, calm, and collected under stress—the ability to “keep your head when all about you/Are losing theirs…”
Mental toughness also includes standing guard at the portals of your mind; making sure that the thoughts, ideas, and emotions that you choose to entertain serve you, advance you toward your life goals. There are things in life beyond our control but our response is always in our control. Those who are fuerte en la cabeza always choose to respond effectively.
“Stepping stone or stumbling block” is often merely a matter of perception and response.
Closing quote:
“As a child, you are not responsible for any dysfunctional programing you may pick up. As an adult, however, you are responsible for the choice to keep it.”