Yeah, and once you have kids it seems to get even worse... on the plus side, not having to wonder "am I doing anything really meaningful with my life?" any more is a bonus. On the other hand, you're forced to face more mortality; but even this has its advantages (c.f. "meaningful" above).
And it isn't a gradual realization. It comes to you rather suddenly. AND THEN you have kids and it accelerates even faster.
When I'm hanging out with my father-in-law, who is in his mid-60s, often reflects on how his fast life flew. Seemed like he "was only 40 a couple years ago".