@littlek,
By "this year" you mean either November or December of 2008, k? You'll have to tell us all the exact time so's we can celebrate with you!
How should you celebrate?
Hmmmmmmmmm ... <thinking, thinking ...>
Anything that you've been thinking you'd really, really like to do, but haven't had the opportunity to do so far? Travel to a particular place? Start work on that painting you've always wanted to paint? Move to Mexico? Etc, etc, etc ..... (Think big!!!)
....Then age 40 is a really good time to do it ... whatever "it" might be!
Be a devil!
Go on!