One analysis I read (linked below) said this poem was about a man who had rejected God, and this battery at sea was the consequence (because, of course, God controls the sea and the weather). It also said the author was contemplating suicide as the only way out of this misery.
The word choices are violent and emotional:
sharp seas mine enemy steereth with cruelness rain of tears cloud of dark disdain despairing of the port
One line (“every oar a thought in readiness”) is beautiful to me because of the way the analysis below described it: That the author was trying to think his way out of this turmoil, like oars trying to right the ship, and yet he could not. Anyone who has ever been depressed or experienced hopelessness knows that trying to get oneself out of it using logical thought is useless.
The end of the poem indicates that the author doesn’t even remember why he’s experiencing this trauma, and also that he has no guide (like the stars) for getting him to safety.
My galley charged with forgetfulness
Through sharp seas in winter nights doth pass
'Twene rock and rock; and eke mine enemy, alas
That is my lord, steerth with cruelness
And every oar a thought in readiness
As though that death were light in such a case;
An endless wind doth tear the sail apace
Of forced sighs and trusty fearfulness
A rain of tears, a cloud of dark disdain
Hath done the wearied cords great hindrance
Wreathed with error and eke with ignorance.
The stars be hid that led me to this pain,
Drowned is reason that should me comfort,
And I remain despairing of the port.
....
Wyatt is talking about despair, and probably means religious despair (the 'sin'