Adults have been known to succumb to the powers of stress throughout their lives not because they have more of it than children do, but because they are not as good at handling it. There is a reason that you do not often see children in a stressful state. While many argue that this is because they have less stressors, this is simply not true. To a child, their problems are just as important as your own. Where they make up the difference however, is the way that they deal with their stress.
Where an adult thinks that things like finger-painting or laying out on the dirt outside is foolish, a child knows that this is a great way to relieve stress and have a bit of fun in the process. The reason that adults often succumb to stress is because they are unwilling to be open to engaging in simple activities that help melt the stress away. Whether you want to acknowledge it or not, people have a need to be playful and whimsical, a need that does not end when you enter adulthood.
You would be surprised how a simple act like swinging on a swing or throwing rocks into a pond can affect your psyche. Even digging around in the mud and dirt can be a spiritual and therapeutic experience that many adults simply will not try at the risk of looking foolish. The truth is, it is foolish to feel stressed when a whole world outside exists to help alleviate it.