the most annoying thing to happen in the history of aoc is when you are trying to wall more to stop their rush and a monk converts your vill and then they're in!!!!
Happened to me the other day and i tried to fight the vill with 2 vills of my own but he beat them both because the monk kept healing him :/
I almost ragequit... from there the game was over.
Most higher rated players on bf will always try to get their scout on the enemy's side of the map. So they know what their opponents will be doing and can anticipate it early on.
For example if you are booming and you see he is setting up eco for a smush u just triple layer stone in feudal. By the time he is castle he'll have to either buy his way into a delayed boom or he'll still smush which shouldn't be a problem to stop 'cause of the time the wall buys you.
If you lose your scout or can't get in to the other side you can always just palisade scan. losing wallers to smush is most of the time a sign you weren't prepared for him :D