The idea that your old habits and thoughts no longer fit into who you are now or who you've become. The lament for your older self: you're brighter, more energetic, everyone loves you self. The self with a light hearted happy go lucky sense of possibility.
But our memory fails us... time and time again. Always thinking that the past was always more fun and easy. It was just as hard then as it is now.
That's the paradox that we all must face. The tragic comedy of life.
If you're not growing however, you must be dieing. And which is worse? Which is better?
Hopefully, you can say to yourself with truth and clarity that you've found happiness and laughed and loved... even for a short while.