Going “against the grain” (or across it) usually implies hardship. It suggests that you've made a move for a reason that compels you put forth some extra effort. ... Usually, we cut a piece of meat against the grain after it's finished cooking and resting, just before serving.

How do you tell if you're cutting against the grain?

To identify which direction the grain of the meat is running, look for the parallel lines of muscle fiber running down the meat, and slice perpendicular to them. For those cuts that have fibers running in different directions, it's vital to “read the meat” and adjust the direction in which you're slicing.

What does along the grain mean?

Look closely at a piece of meat and you'll see that the long muscle fibers run parallel to one another. Cutting across the grain means to slice perpendicular to the fibers, so the fibers in the cut pieces of meat become much shorter, making it easier to chew them.