Whether you're looking for work or want to make the most of any opportunity, the generic advice is to update your CV regularly. I say ignore it! The most important thing is that you keep an updated list of your achievements, training and skills. When you write your CV, you target it to specific jobs. Instead of struggling to remember what you've done, you can search your list of achievements to highlight your strengths in the skills required.
To start your list, I recommend grabbing your CV and copying down your list of education and previous occupations. It's handy to have the dates as a reference. Now think of the skills that you learned from each of these items. These can be specific skills (in my case it would be a list of lab skills), but you should also think about the “transferable skills” that employers love. (There's a list on this careers website).
You should also have a list of ALL of the training you have received. For example, I have a basic food hygiene qualification. It's not relevant to what I want to do but I keep a record of it just in case. If you have received any qualifications or been on a course, write down the dates and the skills you developed.
Don't forget to include any volunteer work you've done, important milestones at work (promotions, improved the company profits by XX%), and other achievements (published an article in Photographer Weekly, learned intermediate Swahili at evening class - no, this wasn't me!).
You'll probably end up with far more than you could fit on a 2-page CV, but that's the point. Target your CV specifically for the job you're applying for, pulling examples of the skills required from the list you've compiled. If you ever want to change career, you probably already have most of the required skills and probably some relevant experience. Having your details to hand will take away the stress of trying to remember and let you concentrate on your application.
Don't forget to update your list when you gain new skills or qualifications!