Well... I dont have a fear of getting old. I do feel like I am physically older because of all the aches and pains. I would imagine with Bipolar... being aware of our emotional rides... also helps us to be aware of our physical body a little more. Also, going through a manic episode may cause you to stay focused on the goal to the extent that you might not realize the stress you are putting on your body. Once again making us feel old.

Is trivial as it may seem... going from 19 to 20 itself may be causing those thoughts. No longer a teenager.... becoming more active in setting out your life plans.
Nobody thinks about going from 33 to 34.... but 39 to 40 ... thats a little different.
For some reason... That first number bothers people... Change it.. and the whole perception of what should be a happy birthday goes out the window.
But a number is just a number..