We can find evidence from the very beginning of Arthur Miller's play Death of a Salesman that reveals how Willy Loman's world has certainly come crashing down.
In Act One we witness how Willy explains to Linda, his wife, how he nearly crashes his car again, and even comes close to hitting a boy. This would be a shocking revelation to a regular person, but it seems that Willy Loman has had trouble for a while. From what we learn, Willy tends to "wander off" in his mind and loses touch with reality, even when he is driving. As a result, he has crashed his car in more than one occasion, one of them with it ending up by a shallow lake. We learn later that Willy, in fact, does wander off in his mind but that the crashes are actually suicide attempts.
Willy: I got as far as a little above Yonkers. I stopped for a cup of coffee. Maybe it was the coffee.
Willy: (After a Pause) I suddenly couldn’t drive any more. The car kept going on to the shoulder, y’know?
Linda: (Helpfully) Oh. Maybe it was the steering again. I don’t think Angelo knows the Studebaker.
Willy: No, it’s me. It’s me. Suddenly I realize I’m goin’ sixty miles an hour and I don’t remember the last five minutes. I’m- I can’t seem to- keep my mind to it.
We know that Willy's world has crashed down because he can no longer bare it. His mind begins to play tricks on him because, otherwise, he would have to realize that he has really wasted his life away, and that of his family, in the pursuit of the dream of being a big-time salesman. In reality, Willy is not that great. Even Linda admits that Willy never was big in his business, nor has made a lot of money.
I don't say he's a great man. Willie Loman never made a lot of money. His name was never in the paper. He's not the finest character that ever lived. But he's a human being, and a terrible thing is happening to him
Another poignant instance of life crashing down comes when Willy tries to get seeds to "plant something" in his small garden. This is probably one of the most significant moments in the play. After all, it is a clear allegory to fact that Willy accepts not having left anything "grounded" for his children when he dies.
I've got to get some seeds. I've got to get some seeds, right away. Nothing's planted. I don't have a thing in the ground.
This is also the climactic moment when, in a hallucination, he tells Ben about his idea of killing himself to leave Biff and Happy his life insurance money.That way, they will be able to start off their dreams in solid ground, unlike Willy.
Conclusively, Willy's breakdown has come slowly but surely. He cannot accept his wasted life, and sees his patterns repeated in Biff and Happy's wrongly-planned dreams. When he finally decides to end his life, it happens after he has made "peace" with his past and his present. In the end, Willy still dies a lonely man with no grand funeral, like he once, falsely, predicted.