Do not tempt my misery,
Lest that it make me so unsound a man
As to upbraid you with those kindnesses
That I have done for you.
No one likes to have to remind others of what one has done for them. Those others should remember and be grateful without being reminded. To have to remind them is humiliating. Antonio, under arrest, and therefore in "misery," asks Sebastian (as he thinks "he" is) to not make him remind him.