It's a necessary restriction. Part of what drives modern anxiety is you don't know the future, so it's necessary that while you get to pick a time period where you have perfect visibility into its future (for example, you know that the cold war doesn't lead to the nuclear apocalypse) the person who lives through that moment can't have that knowledge. If you picked the cold war period, it is necessary that you pick it knowing your cold war self would NOT know that, and would be as anxious as their time and circumstances would make them with the information they would have had then, not the perfect* information you have now.