living in the present

I used to be unhappy until I understood how to live in the present moment. Now don't get me wrong, I'm not talking about being spontaneous to the point of not thinking about the effects of my actions, I'm describing a more philosophical approach to living in the now.
Often it's the close, personal relationships that get highlighted most quickly. And sometimes new meditators report a shift in the way they interact with people around them who they don't know - whether it be the person serving them a coffee or the tourist asking for directions on the street corner.
How do you feel when someone tells you "you've got your whole life ahead of you?" I hope I'm not alone with this - I feel absolutely terrified. There is an internal howl of panic and my subconscious screeches: "What am I going to do for the rest of my life?"