For those tied to imperial, the op's stats are below.
40mi ride
2600' climb.
13.6mph average
Hey OP- I the feeling...mostly. For me it's constant disbelief that normal people can ride routes i ride at 5 and 6mph faster. I say that I'm in good shape and even if I dropped 10# to be in great shape, I still wouldn't be close to the speeds I see. I cant imagine how massive my legs would have to be to average 28-21kph!
I consider anything over 50'/mile to be a solid ride and that means 600m for your 65km ride.
Keep working hard and best of luck catching riding faster!