Shakespeare makes desperate attempt to try and make the dark lady love him. It's both pathetic and manipulative - classic Shakespeare.

Sonnet 140

Be wise as thou art cruel; do not press
My tongue-tied patience with too much disdain;
Lest sorrow lend me words, and words express
The manner of my pity-wanting pain.
If I might teach thee wit, better it were,
Though not to love, yet, love to tell me so;
As testy sick men, when their deaths be near,
No news but health from their physicians know;
For, if I should despair, I should grow mad,
And in my madness might speak ill of thee;
Now this ill-wresting world is grown so bad,
Mad slanderers by mad ears believed be.
That I may not be so, nor thou belied,
Bear thine eyes straight, though thy proud heart go wide.

Shakespeare is head of over heals in love with the "dark lady" but her can see his love isn't necessarily reciprocated.

Sonnet 139

O! call not me to justify the wrong
That thy unkindness lays upon my heart;
Wound me not with thine eye, but with thy tongue:
Use power with power, and slay me not by art,
Tell me thou lov'st elsewhere; but in my sight,
Dear heart, forbear to glance thine eye aside:
What need'st thou wound with cunning, when thy might
Is more than my o'erpressed defence can bide?
Let me excuse thee: ah! my love well knows
Her pretty looks have been mine enemies;
And therefore from my face she turns my foes,
That they elsewhere might dart their injuries:
Yet do not so; but since I am near slain,
Kill me outright with looks, and rid my pain.

Shakespeare talks about ageing and infidelity and LIES in this one. The relationship is getting spicy.

Sonnet 138

When my love swears that she is made of truth,
I do believe her though I know she lies,
That she might think me some untutored youth,
Unlearned in the world's false subtleties.
Thus vainly thinking that she thinks me young,
Although she knows my days are past the best,
Simply I credit her false-speaking tongue:
On both sides thus is simple truth suppressed:
But wherefore says she not she is unjust?
And wherefore say not I that I am old?
O! love's best habit is in seeming trust,
And age in love, loves not to have years told:
Therefore I lie with her, and she with me,
And in our faults by lies we flattered be.