A wonderfully positive post - which is always nice to see.
Noknowldge - I have no wish to single out your answer, but I have to confirm that depression - as in the medical condition as oposed to 'being depressed', can strike absolutely anyone, any time.
One of the major problems for eternal optimists is they have no mechanisms in place to deal with the loss of mental gravity - and often lack the ability to communicate their distress, leaving the friends and family to procalim that the sufferer is 'the last person you;d think of ...'.
It's precisely because people are 'copers' that when they can no longer cope, the suffering is proportionately greater and harder to deal with.
However, nice that no-one has been damning, sarky, unfeeling, 'clever' or similarly inappropriate. of course, if anyone does it now, they will simply be exposed as the idiot that they are!
Let's be nice - it's free and it works for everyone!