I'm assuming he meant by "aggressive mindset" that one must be aggressive in the learning and applying in training aspect. One can easily think in terms of "good enough" because he/she attends training and then applying the learning in a volunteer context like mine. Many people in groups like ours attend training to be involved in roles requiring a certain amount of expertise to accomplish the medical, security, disaster recovery, etc activities. Some folks are just lax in their learning; and now you have to depend on them
