Exercise: It's not just cardiovascular exercise you need to think about (i.e. swimming, walking, dancing) there is also resistance work and stretching. A good range of movement is needed for many everyday tasks such as tying shoelaces, gardening or reaching for something on a shelf. This is a simple stretching routine that can be done in the home.
Eating: Keep a food diary. This will help you become aware of your eating habits. If possible note down how you feel about an hour after eating and see if there is any link between you feeling lethargic or depressed and the food you have just eaten.
Mental wellbeing: Smile. It's hard to be in a bad mood if you are smiling, try it and see.
For more details of NHS Self Care Week 2011 and information to help make healthy lifestyle choices please visit NHS Choices.