How to overcome depression

Ever felt worthless, numb, sad, helpless, with no hope for the future? How does one deal with such feelings, especially when the one person you love is the main reason you feel like this? How do you unlove that person and move on with your life? How do you let all the pain and hatred go? How do you move on? Because at this stage it seems almost impossible when you’re in so much pain. How do I choose myself for once and act like none of this ever happened? How do I let go?