Here are some words of Martin Amis's apropos his friend Christopher Hitchens:
He was someone with exceptional love of life and since he has died he has bequeathed his love of life to me. I feel the obligation to value every moment because he is not there to value it... Your wonder of life increases towards the end because it is tinged with a leave-taking feeling that it's not going to be there for very much longer.
Recognition! You get to this point where you not only enjoy things (when you do) but also have a second-order response, along the lines 'I'm enjoying the day (this book, movie, walk, get-together with family, friends etc), and that's good because my time is now (more) limited, and I must make the most of it.' Probably it comes for everyone at a different point in their lives, but I know exactly the day, just over nine years ago, when I started to have this background consciousness, so to say noticing what used to be just the regular events of life.
Amis's reflection got me, then, to thinking about all that expanse of time - youth, relatively speaking - when I didn't used to do the noticing thing. I mostly just did first-order stuff, ordinary living, and enjoyed it, or not, but in any case got on with it without the extra layer, without looking at it all under the self-imposed injunction to thank my lucky stars.
And this prompts the question: would it be better to start 'noticing' earlier? If you did, you wouldn't take all those years of life for granted, you'd appreciate them more. But, on the other hand, then you'd be like an old(er) person before your time. Part of being young is the feeling of having a long, long time ahead of you. If there was already a second-order narrative in your head, your youth would be grey at the temples. It's an impenetrable conundrum.