Firstly, low self esteem and depression are not necessarily related. A person can have low self esteem and not be depressed and it is possible for someone with depression not to have low self-esteem, even if low self-esteem is one of the symptoms of depression.
Low self-esteem is about self worth, whereas people with depression tend to think badly about all things, not just self-worth.
Treating problems of degraded self-esteem needs to be worked along with the approach to the depression, it's not okay to treat them all together.
With self-esteem issues, it's very important to remember that everyone has failures, bad days, depression of some level, everyone looks at themselves in the mirror and goes yuk.
Understand that self-esteem and depression make you feel terrible, but you are not terrible, you are not your illness and you are not the person you currently see yourself as. In fact, you would probably be surprised at how highly people think of you.
Depression is a state of acute worry or hopelessness. When one is depressed, he or she becomes overtly pessimistic and is not able to concentrate. A depressed person is not able to sleep well and suffers mood disorders. He is sunk in a gloomy state of despair and fails to see the bright side of life.
Why do people feel depressed? When a person does not get what he or she wants to achieve, a sense of sadness prevails. It gives way to frustration, anxiety and worry. The confidence of the person crumbles and he or she feels that they do not have the ability to perform the second time too. The failure attitude makes one fearful about giving life a second chance. For example, a person who is rejected in love once may feel inadequate. His self-esteem, which takes a beating because of the rejection, makes him wary about proposing another girl. However it is important to know that no one has achieved success in the world without failure and rejection. These are in fact, the stepping stones of success. It is only your negative thoughts which can hurt you, not the situations. You are not a failure, unless you have made your mind to throw the towel in.