If you feel unhappy because of something that has happened to you, then probably the ideal thing is to talk about it with sympathetic friends or family. if that is not possible, then at least you need a chance to go somewhere quiet where you can think. To write down the situation and how you feel about it is also very helpful, as this can help you identify the problems and start finding a solution.

However, if you often feel unhappy and can't find any real reason for it, it is possible that you need help. It's quite normal to feel low spirited or lacking in energy now and then, and for most of us a quiet walk in the countryside or a park, or even an afternoon just relaxing with a book or some music, is enough to make us feel better. If this kind of thing doesn't help you, you should probably look at the symptoms of depression to see if you think you need to talk to a professional - i hope not, but it's a good idea to be well informed.