Someone once said the secret of happiness is having someone to love, something to do and something to look forward to. There is probably some truth in this, although it does not mean you have to have an adoring spouse or partner, a high-powered job and a world cruise coming up to enjoy life. The 'someone to love' can be a friend, relative or pet, and the 'something to do' and 'something to look forward to' could be just about anything you enjoy. But even if you have those three 'somethings', there may be times when you don't feel very happy. Our mood can be affected by all sorts of things, including lifestyle, past experiences and genetic factors. Scientists think that people who always seem to be in a good mood may simply have naturally higher levels of certain substances - endorphins (types of hormone) and the neurotransmitters (dopamine and serotonin). These are released by the brain and make us feel good when we are enjoying ourselves or when som...