A depressed person tends to denigrate themselves, feel hopeless and hold a very pessimistic view of their future.
Inform your GP of your depression to rule out medical issues and in case medication is required. Be open to antidepressants especially if your depression is severe (debilitating).
Engage in aerobic activity (antidepressant effect). Increase your level of support including social contact and contact with nature and animals.
Increase pleasurable activities.
Prevent relapse through identifying what leads to the low mood. Maintain physical activities, social contact, practice mindfulness.
Use CBT thought records to process negative thoughts. Work on core beliefs.
Consider evaluating your depression with an accredited psychotherapist.