I happened to speak about this to an internationally certified Montessori teacher. She talked about what they do at school when they find the child is stressed. Apparently getting the child to drink some water calms him down. Diverting their attention with some physical activity helps. Pressing your palms against a wall, dancing to some peppy music, etc. also help.
One thing I have learnt is that asking for help is an effective way to solve problems. To do that you need to have a reliable network of friends whose views you respect. You can’t develop this overnight. As a parent, make sure you have a network of parents of children in more or less the same age group as your child. Talking to one or two of them could help.
Search the net for “How to help your child cope with stress”. You will find several articles, blogs, papers and books on the subject. Put together a collection of things that you can try. Over a period of time understand what works for you and your child.
Life around us creates its own pressure all the time. All of us will be stressed sometime or the other. Being prepared with coping mechanisms is a better way to help our children than subjecting them to ‘trial-error’ when they are stressed.
Two words strike me as most important. Listening and compassion. If we practise these regularly with our children it will be a big advantage in helping them cope with stress. You will then become their natural ‘go-to-person’ to talk to.