I heard that advice many times, agreed with it, but still didn't really feel the weight of it until now, as my kids reach that range. It's bittersweet -- you see them blossoming into ever more amazing and beautiful versions of themselves, and you realize that you have even less time to be around them.
> The best advice I ever got was to internalize this: “the days are long but the years are short”.
100%. I can't count the time I picked up my infant / toddler and simply held then and felt their warmth. I also can't remember the last time that happened.