Before you can convince an employer that you are the perfect candidate, you must first convince yourself. Remind yourself of all the fabulous traits and specific value you have to offer a company.
Your experience, reliability, wisdom, common sense, patience etc. are all valuable assets you've developed over the years. And these are traits many young folks don't yet have in abundance.
Don't be defensive about your age. Go into your search with a positive, confident attitude about all you have to offer. This will make you feel and appear younger. And get you the job.