Willy is not "crazy" as in "insane" but he is one of the most washed-out, non-affirmative characters around. He is unable to take control of anything and seems to be a victim of life itself. Between the precarity of his job and his family obligations, Willy is held in stalemate.
At first Willy thinks looking smart or positive thinking is the key to success. He truly believes that a little "luck and pluck" Horatio Alger style will bring him clients and contracts. As his short quips in the dialogue portray, Willy is looking for a magic formula, a foolproof recipe, a quick fix to resolve his problems - but to no avail.
Ironically, his suicide at the end of the story (in hopes of procuring insurance money for his family) is the only time Willy Loman ever manages to assert himself. Athough he has been a failure as a parent, husband and businessman, he manages to "provide" for his family.
Was Willy really that desperate or had his life simply become a humiliation? Even his death is an anitclimax (it isn't even portrayed, but just alluded to); life goes on for his wife and sons, and finally they are better off (at least financially) without him.