They think when they are supposed to act and act when they are supposed to think. They ultimately put their lives in jeopardy because of their inability to make informed, logical decisions. Shakespeare's Hamlet is an example of the latter person. Throughout the play, Hamlet struggles with an unbalanced psyche that causes his indecisiveness. The scenes where he is emotional, most of which are when he is giving a soliloquy, are the scenes where he does the most thinking; and by contrast, the scenes where he tries using his intelligence, be it for his own good or for trying to outsmart others, he appears overly emotional. Hamlet, in all of his greatness and scheming, does not have a balanced psyche, and ultimately, his inability to keep his rational and emotional sides separate is what leads to his death. .
One of the first examples where we see an imbalance in Hamlet's psyche occurs in Act 2, Scene 2 of the play. Hamlet, while talking to Rosencrantz and Guildenstern, makes the comment, "Why then "tis none to you; for there is nothing either good or bad, but thinking makes it so. To me it is a prison" (2.2.245-246). Hamlet deems murder, the subject of his conversation as well as a highly emotional act, as neither good nor bad. He goes on to say that any stigma associated with or justification of murder is the result of overanalyzing and thinking. Hamlet, in this one statement, manages to take an emotional act, strip it of any psychological associations (rational or emotional), and then justify it as a rational act. This in and of itself shows Hamlet's lack of mental balance. How he can take something that it so clearly one thing, and in one phrase turn it into the total opposite only proves that his psyche is not stable. This evident lack of balance of his psyche is the tip of the iceberg of Hamlet's instability. .
By Act 3 of the play, Hamlet is struggling not only with melancholy and mental instability, he is struggling with having to avenge his father's death.