Then hate me when thou wilt; if ever, now;
Now, while the world is bent my deeds to cross,
Join with the spite of fortune, make me bow,
And do not drop in for an after-loss:
Ah! do not, when my heart hath ’scap’d this sorrow,
Come in the rearward of a conquer’d woe;
Give not a windy night a rainy morrow,
To linger out a purpos’d overthrow.
If thou wilt leave me, do not leave me last,
When other petty griefs have done their spite,
But in the onset come: so shall I taste
At first the very worst of fortune’s might;
And other strains of woe, which now seem woe,
Compar’d with loss of thee, will not seem so.
In plain English
If you're going to hate me, do it now—while I'm already battered by the world's cruelty. Don't wait until I've weathered this storm and started to heal, only to strike me down again when my guard is lowest. That second blow would be worse than any I'm suffering now.
If you must leave me, leave me at the start, not at the end. Get it over with before other smaller sorrows pile on. That way I'll face your loss head-on, at full force, rather than as the final weight on an already broken spirit.
Here's the brutal honesty: your abandonment would hurt so much more than anything else life could throw at me that all my other griefs would pale beside it. So if it's coming, let it come now—let it be the worst thing, not the last thing.