I agree that panic is not a useful emotion and it's better instead to direct that energy towards preparing for the worst case scenario whose outcome you can effect.
Get any medications, supplies, electrolyte mixtures, etc together. Test your heat source and your back up heat source and make sure they're functioning normally just in case. Make sure you have their feeders, waterers, etc. cleaned and prepped. Take the time to read up on how to safely rehab these chickens based on different potential scenarios (weak and lethargic, starved but active, healthy just shipping stressed), and have a back up plan for contacting the hatchery in case of disastrous results.
If you prepare well, it's much easier to remind yourself that no matter how the chicks arrive you have a plan of action for moving forward.