Hamlet, beholding the victim of his indiscretion, excuses himself thus:--

I must be cruel, only to be kind.

The cruel deed he has done, he palliates with the remark that
lovingkindness has forced him to it. Love of her God also forced
Catherine of Medicis to the massacre of St. Bartholomew.

Thus bad begins, and worse remains behind.

Yes; worse is coming! Hamlet knows that he is to be sent to England;
that the letters are sealed; that his two schoolfellows whom he trusts
as he will adders, bear the mandate. What does he do to prevent further
misfortune?

He rejoices that--

they must sweep my way,
And marshall me to knavery. [47]

He enjoys, in advance, the sweet presentiment of revenge which he
intends taking upon them. He lets things go without hindrance:--

Let it work!
For 'tis sport to have the engineer
Hoist with his own petard.

He enjoys his own crafty policy which shall blow his school-friends,
Rosencrantz and Guildenstern (who yet, so far as he knows, have not
been guilty in any way towards him!) 'at the moon:'--