I came across this on Facebook some time ago, and have been debating on whether or not to repost it here, as I'm a little wary of getting too into the habit of presenting non-original content. Then I remembered that I don't actually care about that, so here it is. The link to the original article is here (link). Everything that follows is a verbatim repost. Cheers.
James K. Flanagan: A Grandfather's Last Letter To His Grandkids