Double-Click The Fill Handle

I work in Excel analyzing data ... a lot.  Copying and pasting a formula into thousands or ten of thousands of rows has been a slow, thorn-in-the-backside, operation for years.  Then today I run across this "fill handle", which reduces my efforts to a single double-click.  I don't know if I want to jump for joy at all the hours I'll save or weep a bucket of tears for all time I've already wasted.

https://miketips.wordpress.com/2011/09/09/5-things-excel-fill-handle/