In the opening scene of The Merchant of Venice, it's Antonio who's feeling depressed. What makes it worse is that he doesn't seem to know why. Salerio and Solanio try to help out by offering their own suggestions as to what may be bugging their friend. Salerio thinks that Antonio might be worried over his merchant ships. It's a hazardous business and ships and their valuable cargo are often lost at sea due to pirates, stormy weather, and all manner of unavoidable hazards. Salerio tries to reassure Antonio that, as his ships are so big, they will fly across the ocean, dwarfing the smaller ships and boats as they sail majestically past:
Your mind is tossing on the ocean, There, where your argosies with portly sail, Like signors and rich burghers on the flood—Or, as it were, the pageants of the sea—Do overpeer the petty traffickers That curtsy to them, do them reverence As they fly by them with their woven wings. (act 1, scene 1)
Salerio then tries a different approach. Instead of reassuring Antonio over the fate of his ships, he tries to empathize with what he thinks is his predicament. He tells Antonio that, if he were in his position, he'd never stop fretting. Whatever he did during the day would act as a reminder of what could happen to his ships at sea: blowing on his hot soup would make him think of his ships being buffeted by a storm; every time he looked at the sand in an hourglass he'd have terrible visions of ships being wrecked on sandbars; and he'd think of dangerous rocks when he went to church and saw the stone it was made out of.