I think it is a combination of nature and learning. I do remember everything very vividly and it helped me a great deal through school and college. But as I grew older I began to remember more through an understanding, application and connectedness.
I find I am not just able to remember but able to teach my students to remember better through use of narratives, examples and memorable quotes. I try to use metaphors, analogies, connect with whatever the students are interested in to make them see the link to what I am trying to teach and anchor that memory. The feedback from students has been very good!