This is a part answer, which only refers to the concept of resilience.
One of the first studies that invesigated resilience was the Kauai-Study, which was a longitudinal study of a cohort in Hawai to investigate the cognitive, social and physical development of children. (Werner and Smith, 1982) Of the children who had to deal with a couple of risk factors from birth on, about a third managed to overcome the obstacles later in life. This led to the formulation of a theoretical concept of resilience, which included vulnerability of the child as a main risk factor and external stress on one side, and social support and ressources within the child on the other side as elements. These elements interact with one another and influence the development of a child. In this sense, resilience was defined as a potential, or maybe kind of like a trait. If there is enough resilience, a "good" development will be possible in spite of a difficult environment. The second thing to notice is that resilience originally was geared towards children.
The concept of resilience has been expanded to adulthood later. Apparently, though, this has led to some problems concerning the definition, since the original conception was explicitly concerned with development in childhood (Luthar and Cicchetti, 2000). The article of Leipold and Greve (2009) integrates different proposals to solve this problem. In their model, resilience, development and coping are linked. Development is seen as coping with all kinds of demands and stressors, and resilience is seen as succesfully doing so. Note that in this definition, resilience is very different from the one that I have given above.
To get to your question: an "addiction to sympathy" might be seen as a lack of resilience, but not in the sense of a trait. It can be seen as the lack of a process as conceptualized by Leipold and Greve (2009). This also leaves open the possibility that the process might "kick in" at a later stage in development, which not only makes sense but is also what you have experienced yourself.
Leipold, B. & Greve, W. (2009). Resilience. A conceptual bridge between coping and development. European Psychologist, 14, 40-50.
Luthar, S. S., & Cicchetti, D. (2000). The construct of resilience: Implications for interventions and social policies. Development and psychopathology, 12(4), 857-885.
Werner, E. E. & Smith, R. S. (1982). Vulnerable but invincible: A study of resilient children New York: McGraw-Hill.