Counting
Hakkai has a watch in his pocket that he doesn't look at. It's only correct twice a day, after all. It's not very old, not very valuable, and the glass face is broken, but it stays in his pocket because he doesn't need it when he doesn't think of it.

The watch has stopped, but Hakkai is still counting. He counts the days from (each and every) time he should have died, and he counts the miles on Jeep's meter, and he counts the bullets left in Sanzo's gun (five, four, three, two), and he thinks, I only need one.