While everyone occasionally feels sad or "blue," these feelings tend to pass rather quickly.
By contrast, someone with depression experiences extreme sadness or despair that lasts for at least two weeks or longer. Depressed individuals tend to feel helpless and hopeless and to blame themselves for having these feelings. Depression interferes with activities of daily living — such as working or concentrating on tasks, or even eating and sleeping. Other possible symptoms of depression include chronic pain, headaches or stomach aches. Some people may feel angry or restless for long periods.
People who are depressed may become overwhelmed and exhausted and stop participating in certain everyday activities altogether. They may withdraw from family and friends. 
A combination of genetic, chemical, biological, psychological, social and environmental factors likely contributes to the disorder. 
How can I help you?
Many research studies have demonstrated that psychotherapy, or talk therapy, is effective for treating depression and relieving symptoms experienced by individuals who suffer from depression. Psychological treatments may prevent a person with milder depression from becoming more severely depressed. And although a past history of depression increases the risk of future episodes, there is evidence that ongoing psychotherapy may lessen the chance of recurrence.
My aproches are CBT and ACT Therapy. With CBT Psychology treatment help people with depression to change negative patterns of thinking and improve their coping skills so they are better equipped to deal with life's stresses and conflicts.
ACT is thought to work by helping people to stop avoiding difficult experiences, especially by ‘over thinking’ these experiences. Over thinking occurs when people focus on the ‘verbal commentary’ in their mind rather than the experiences themselves. ACT encourages people to accept their reactions and to experience them without trying to change them. Once people have done this, they are then encouraged to choose a way to respond to situations that is consistent with their values, and to put those choices into action.