And the wall falls down

So, have you ever built a wall out of those little wooden ABC-blocks? It's not exactly sturdy. So, once you get it up to a certain height, it doesn't take more than a stiff breeze to knock it over. You get it to that point and you're watching to make sure nobody comes to close cause it took you so long to build it and don't want it to fall over. After a while, though, you start looking at the wall and you start thinking about what it would take to make it fall. You figure out that all it takes to destroy the whole thing is to disturb one little block and the whole thing comes crashing down. After that, you knock over the rest of it and have to start over again. Last night, I disturbed one of my blocks. It was careless and now I get to start all over.