When you are younger, it is easy (and natural) for youthful vitality to carry you through the years of exploration and adventures. It's like riding a wave. The velocity doesn't often allow for you to take time and really inspect life as it rushes by.
But hit fifty and, wow, things change. No more free rides, no more yelling and screaming sans souci. Contemplation descends upon your existence. You cannot ignore things as easily. You cannot ignore the throbbing truth of reality. This too is a natural occurrence. You are more or less ready for it.
Usually a bit less than more.
So you have to dig deep. Truth is harsh. Things don't turn out as you imagined. Romance fades. Notions of beauty and magic wither. And yet, you can not let yourself become jaded. You have to find what goodness you can amidst the wreckage. You have to not only continue to survive but you have to use whatever skills and energy you have to somehow rebuild a version of yourself that is less idealistic, less consumed and consuming, less charged. You have to accept your mortality. You are reminded of it more often now.
You need to see the bigger picture. Divest from ego. Jettison a large trunk of self serving activities and realise that the time for taking is gone and the time for giving back is nigh. This will be a large part of your salvation. This will make the sting of the realisation of lost youth hurt less.
There is still time to grow. Still plenty to enjoy. Sink not into the morose. Be not a victim. But do not ignore stark truths either. You are heading towards the exit now. But on your way out you can still slap a high five, scratch a pithy caption on the wall of the corridor. You can even blow a fucking hole in the wall and make a window for those to come!
So lament not. Feel the sorrow. Express it. Release it. And accept the kiss of each morning's sun with a steady, kind and open heart. It's a new day. A new day for everyone.