Sometimes my brain hits me with the most mundane memories, and even those bring comfort & nostalgia at times. Trying to appreciate all the little things and enjoy the moment.
I agree with your statement, @crummysocks is 20 and at the start of a long journey, but it does not feel that way to him, it didn't to me in my 20s either.
Honestly, the oldest I ever felt (feeling that time was slipping away) was 25 and that was last century. It took me to 30 to realise life was just beginning.