An ongoing refrain of mine is, "Get your stories down!" I have benefited greatly from letters and other written records of people's lives in the past - records that can't be found on Ancestry or FamilySearch - or anywhere else, for that matter.
However you are comfortable recording yourself - in a blank paper journal, in a smart phone video, on a tape recorder - just get started. FamilySearch provides a list of 40 journal prompts in case you find it intimidating to get started.
You'll enjoy the benefits of journaling and your descendants will reap the benefits of your unique perspective on your life and times.