How do I keep up the pace picking orders all shift?

Speed and accuracy came to you with time, and now the real test is not skill but endurance. That is a different kind of hard. Your hands know the work; it is the long hours that grind you down. There is no shame in that. A body is not a machine, and pretending otherwise only wears you out faster. Stop treating the whole shift as one long sprint. Break it into smaller stretches and give yourself small resets inside them. Drink water before you are thirsty. Loosen your shoulders between picks. These sound too simple to matter, but the small things are what carry you across ten hours. Today, pick one point in your shift, maybe the middle, where you usually fade, and plan a real pause there. Two minutes, standing still, breathing. Guard that pause like it matters, because it does. Lasting the shift is its own skill, and you can learn it the same way you learned the rest.