Madness in Hamlet
Hamlet's choice to put on an "antic disposition" leads to his downfall; it is a tragic error in judgement (hamartia) which destroys his relationship with Ophelia and Gertrude. It is Hamlet's hubris. Another result from Hamlet's peculiar actions, is that in his own mind he begins to believe that he is mad. It is unfortunate that Hamlet's plan did not succeed; not only did it lead to his own downfall but he had to witness the downfall of all of the people he loved.
With his choice to put on this act of antic disposition, he takes the risk of losing close touch with his loved ones. With his actions of insanity, he drives Ophelia away from him and this eventually leads to her suicide. Ophelia is greatly saddened when Hamlet continues to push her further and further away. Hamlet commands her to go to a nunnery and this is the point where she believes he is mad.
O, what a noble mind is here o'erthrown! ( III; i; 147)
When Hamlet's act continues to unfold, Ophelia begins to feel very betrayed by his love. With only her feelings of rejected love and betrayal left she takes her own life.
Young men will do't if they come to't.
By Cock, they are to blame.
Quoth she, 'Before you tumbled me,
You promised me to wed.' ( IV; v; 60-64)
It is after the death of Ophelia that Hamlet realizes his true feelings for her. This is another contributing factor that leads to Hamlet's own downfall.
This tragic error in judgement leads Hamlet to destroy his relationship with his mother, Gertrude. By faking this madness he makes himself a less believable character. When he attacks his mother with many insults, she does not take his word seriously. This is the result of her believing that he is not well.
This is the very coinage of your brain.
This bodiless creation ecstasy
Is very cunning in. ( III; iv; 138-140)
Gertrude truly believes that Hamlet is mad and she is angered because during this madness, he kills the innocent Polonius. This makes Hamlet erratic.
Mad as the sea and wind when both contend
Which is the mightier. In his lawless fit,