Another factor apart from introversion/extroversion that may play some part in this type thing is neuroticism/emotional stability. People high on the neuroticism scale often find themselves in short supply of the happy chemicals. Neuroticism is relatively high prevalence of negative emotions. Neuroticism can be a survival advantage in some ways as it means greater sensitivity to threats. For example, neurotic people tend to pay closer attention to their own health and that of those close to them.
I don’t consider myself neurotic but I’m definitely unstable and quite aware and sensitive to everything around me. I’m always on the lookout! Though it’s definitely not all bad, especially for security reasons like you mentioned, and for example photography where you rely on finding interesting subjects and light to capture.
Neuroticism is a purely technical term from the five factor model of personality. The model uses groups the following five factors extroversion, conscientiousness, agreeableness, neuroticism, openness (to ideas, experiences etc.).