Stress
You're at least partly responsible for the structural integrity of your buildings. If something goes wrong, you may be held liable if there was faulty design, such as a stairway banister made out of chainsaw blades.
You'll have to work long hours and meet strict deadlines, and you'll drive yourself nuts trying to please your clients. They pretty much live to make your life miserable. And you have to rely on the opinions of many people up and down the food chain to execute on your designs.
Sometimes, they execute poorly and ruin things. But in a design flaw like the core sample problem, it's you who is blamed. And sued. A big part of the stress of the job is finding people on whom you can rely when the chips are down.