Toy designers have the stress of working under conditions where they have to perform to earn a living. Designers who work for toy manufacturers are paid a salary. They know that to continue to be paid that salary they need to earn the company money by designing toys that sell.
Stress can also come in the form of performance anxiety when you are required to stand in front of a group of representatives from the company to try to convince them that your idea will sell because it is fun, safe, will appeal to children and parents, and will have good cost to profit potential. Those afraid of public speaking need not apply.
Independent toy designers may have even more stress, knowing they are investing their own time and money into the development of a toy idea, and that failure might mean losing all of that investment. However, on the bright, shiny side, success in the toy world can mean a huge payoff.