During a typical grooming workday, you'll see at least two stressors rear their ugly little heads. First, you'll be giving baths and haircuts to very different animals. The lab and boxer owners will probably be happy to have their dogs clean, so they'll be easy to please.
On the other hand, you'll have the poodle and Yorkie owners who insist on a show-quality cut even though they're not paying for one. They don't want a hair out of place, and they'll probably want the dog's nails painted, too.
Although each groomer plans their day differently, you'll probably have pets in different stages of completion throughout the day. While your bather is shampooing one, another pet will be getting her personal blow-drying treatment. You'll be finish-clipping and scissoring another animal before you give still another her final brushout.
Here's the point: You've promised each owner a specific pick-up time, which might not allow for mishaps that occur along the way. You don't have a bather? That means you have to wash the pet(s) yourself. If a dog freaks out with a cage dryer, you might have to hand-dry him, which clearly isn't built into the schedule.
If a freshly groomed cat has an accident on the table, guess who mops up both the table and the kitty? All these delays add up, sort of like a snowball crashing down a hill. At the end of the day, you'll have to tell the owner(s) why Fido isn't ready yet. Take a deep breath, squeeze your stress ball, and get ready to face the music.