According to Traditional Chinese Medicine (TCM) theory, we all consist of yin and yang. Yin enables us to be calm, still and restful. Yang enables us to be active, awake and energetic. Children are said to have "insufficient yin" which is why they are constantly active, moving around and demanding attention. As the day goes on, and as a child becomes more tired, they use up their yin energy. This means that the later they go to bed, and the more tired they are, the less calm, still and restful energy they have available in order for them to be able to get to sleep!
It is often hard for our babies and children to avoid being overtired with the very full and stimulating lifestyles we all tend to lead in the 21st century in the West. But it can help the entire family if we, as parents, try to make sure our children go to bed on time and don't get overtired. Not only do bedtimes generally become easier, but most parents notice that their children actually sleep better if they are not overtired. Not only is this good for their health (and the parents health and sanity!) but it usually has a positive impact on a child's behaviour. Children are not generally able to cope with a lack of sleep in the way that we learn to as adults.
It's a simple change to make - but if you think your child is chronically overtired, and bedtimes are usually not fun for anyone, spend a week trying to bring bedtime half an hour forward and you may well be surprised at the benefits for everyone!