As you go about your day, try breathing into your belly. Try to expand your abdomen with each breath. If you can, try to breathe in and out through your nose. Let this breathe give you a way to focus your breathing. Breathing this way naturally relaxes the body and helps release stress.
Here are two great articles on belly breathing:
http://www.gooddaygoldfish.com/blog/2012/6/24/diaphragmatic-breathing.html
http://www.webmd.com/balance/stress-management/stress-management-breathing-exercises-for-relaxation
8-3-1 yoga 