Keep a file with achievements, kudos, and numbers. Make sure you update regularly - and keep the information in a secure location! One of the biggest challenges of creating a strong resume is unearthing one's best achievements, kudos, numbers, and results. In a long tenure - of for jobs more than a few years ago, this becomes exponentially more difficult.
So I recommend that you start keeping a file of career highlights. Use it to remember the numbers, keep an eye on the achievements and collect kudos.
And it's always a good idea to keep that on a personal device - I've had clients who were laid off, and locked out of their workstations and email before they could retrieve the necessary information to support the next career move.
I'm not, of course, suggesting using this approach for anything confidential - just as a memory tool. So when you do go to write your resume - or call me to do it - the information will be easily available. Trust me. This is way easier than trying to remember how much money saved on an initiative 10 years ago.