Student or Learner
Quoted from Academy Street by Mary Costello.
"As she walked along the Manhattan streets she felt a sudden elation. She started to see possibilities everywhere, and it was this feeling of possibility容ven if she did not always avail herself of it葉his vibrancy and passion that were essential to life. Perhaps that was the very source of her anxiety, she thought, the mark of all anxiety: the acute awareness of the endless possibilities that can simultaneously imperil and enhance us, and all that might be lost or gained. And the terrible tension that exists when everything hangs on a moment, that moment when one may take a leap of faith, or not. It is choice, then, she thought, freedom of choice, that is the cause of all anxiety."
I am not sure the meaning of 'mark' here. How come a thing was 'the source' ans also 'the mark' as well?
not a teacher
As I understand the passage, she is speculating that her acute awareness of the endless possibilities which her circumstances provide, may be not only the source of her current anxiety, but is perhaps a mark (characteristic, trait) of all anxiety. Her conclusion is that it's the tension associated with freedom of choice that is the cause of anxiety.