Getting Old

I turn 35 this year and for some reason I have been a little obsessed with how fast time seems to be passing. These first 35 years have flown by and I think that if the next 35 come and go as fast, I will be 70 years old before I know it. It makes me a little anxious. I don't feel 35, I don't act like 35, I'm not mature enough to be 35, how can I be 35. 35 is only 5 years from 40 for crying out loud and I'm certainly not mature enough to be 40. In 20+ years will I have enough to retire, what happens if I don't, where will I be working, living and on and on, my mind won't stop. It makes for a pretty interesting walk to work. I'm feeling (and this isn't breaking news) like for the first time I really understand how short our lives are. This whole train of thought ends up being rather trite, "Enjoy every minute," blah blah. The thing is I think that I have up until now been very aware of every minute and how fleeting our time is so I'm not sure where this age anxiety is coming from. Is this some sort of early mid life crisis?