How wonderfully Shakspere in _Othello_ portrays the wretchedness of the suspicious man.

One reason why Iago so hated the Moor was that he suspected him: the thoughts whereof Doth like a poisonous mineral gnaw my inwards, And nothing can or shall content my soul Till I am even'd with him.
How graphic the simile, "gnaw my inwards;" it is the perpetual symbol of worry; the poisonous mineral ever biting away the lining of the stomach; just as mice and rats gnaw at the backs of the most precious books and destroy them; aye, as they gnaw during the night-time and drive sleep away from the weary, so does suspicion gnaw with its sharp worrying teeth to the destruction of peace, happiness and joy.
Then, when Iago has poisoned Othello's mind with suspicions about his wife, how the Moor is worried, gnawed by them: By heaven, he echoes me, As if there were some monster in his thought Too hideous to be shown--( To Iago) Thou dost mean something.
I heard thee say even now, thou lik'dst not that, When Cassio left my wife; what didst not like?
And when I told thee he was of my counsel In my whole course of wooing, thou criedst 'Indeed!' And didst contract and purse thy brow together, As if thou then hadst shut up in thy brain Some horrible conceit.

If thou dost love me, Show me thy thought.
And then we know, how, with crafty, devilish cunning, Iago plays upon these suspicions, fans their spark into flames.

He pretends to be doing it purely on Othello's account and accuses himself that: it is my nature's plague To spy into abuses, and yet my jealousy Shapes faults that are not: and then cries out: O beware, my lord, of jealousy! It is the green-eyed monster which doth mock The meat it feeds on.

That cuckold lives in bliss Who certain of his fate, loves not his wronger; But, O, what damned minutes tells he o'er Who dotes, yet doubts, suspects, yet strongly loves! There, indeed, the woe of the suspicious is shown.