Fear.

Despair takes heart, when there's no hope to speed:
The coward then takes arms and does the deed.

No wrath of men, or rage of seas,
Can shake a just man's purposes;
No threats of tyrants, or the grim
Visage of them can alter him;
But what he doth at first intend,
That he holds firmly to the end.

None goes to warfare but with this intent -
The gains must dead the fears of detriment.

Evil no nature hath; the loss of good
Is that which gives to sin a livelihood.

When fear admits no hope of safety, then
Necessity makes dastards valiant men.

In all thy need be thou possess'd
Still with a well-prepared breast;
Nor let the shackles make thee sad;
Thou canst but have what others had.
And this for comfort thou must know
Times that are ill won't still be so.
Clouds will not ever pour down rain;
A sullen day will clear again.
First peals of thunder we must hear,
Then lutes and harps shall stroke the ear.