Is retirement investment worth it?

I recently signed up for a retirement investment plan in which I can receive my investments when I am 65. I am 18 now. Apparently my plan involves making fortnightly contributions to my investment accout through money I will earn in the future. I am wondering if it is that important to make retirement investments, I mean, wont most of the money I need be spent when I am young and healthy and able to do things? Once I am 65 I wont have the strength to hang glide or go hunting or other kinds of activities that require money. I am very naive when it comes to the idea of money, business and the like. Enlightenment on the subject will be greatly appreciated.