The years between fifty and seventy are the hardest. You are always being asked to do things, and yet you are not decrepit enough to turn them down.
- T.S. Eliot

Forty is the old age of youth; fifty is the youth of old age
- French proverb

You're half way there!

I have enjoyed greatly the second blooming... suddenly you find - at the age of 50, say - that a whole new life has opened before you.
- Agatha Christie

After fifty everything that doesn't hurt, doesn't work.

50 is nifty.

After a man is 50, you can fool him by saying he is smart, but you can't fool him by saying he's pretty.
- E.W. House

Hope the next half century brings you as much happiness as the first half.

You're almost a senior citizen.

Happy half century.

Still nifty at fifty.

Happy 50th Birthday.