Turning fifty feels like a milestone birthday in a way that you thought 30 and 40 might be but weren’t.
In your 30s you still possess youth, so in your early-to-mid 40s (and by “mid” I mean 48) you can tell yourself that since you’re not that far out of your 30s you must still be young. (Aided by equal parts optimism and delusion, it’s creative accounting at its finest.)