One of them must be: When all the doctors seem younger than you.
When you first wish you could have another chance at life. (The people that never do this don't count.)
When your children come to you for advice. (After years of sticking their fingers in their ears, when you tried to advise them before.)
When you first stood up to pressure, knowing you would suffer a personal loss.
The inner knowledge that "I am now a woman, not a girl." (Of course, this is more upsetting for those who began as boys...)