Finding a job over 40 can be a challenge. You have to stand out from the crowd of qualified applicants half your age. Use your assets that come with age. Confidence is an easy attribute that younger applicants can try to fake but should come easy for you. At 40 you know who you are and what you can accomplish. There's no guess work there. I find that interviews are a breeze because I don't feel intimidated because I know there are lots of other options out there.
Also, be picky. Know exactly what you want to do and go for it. Don't settle. There's no time for short changing yourself.