I'm actually going through the same problem with a specific sin as well. I remember I had this one specific problem, and a scholar told me to PHASE out. Slowly decrease that sin until you absolutely diminish it. You should have in the back of your head throughout the phasing out that you want to get out of it as soon as possible. Imagine your parents, or your family, and Allah Ta'ala watching over you at all times. Would you do the same thing while they were watching?
I have an idea of what sin you are speaking of, but I will avoid guessing. I will pray for you, and I ask you to pray for me in turn. We are related Islamically, and hold mutual love for each other. Do not fear, for Allah Ta'ala is the MOST Merciful to those who are sincere and true.
We all have our ups and downs, and we all get depressed sometimes. Most of us try to cover it up, because your external will work into the internal. That's why they say to keep clean, and "cleanliness is half of Imaan". When you feel good on the outside, Inshallah you'll feel good in the inside as well. Likewise, if you feel good in the inside, you should Inshallah feel good on the outside.
May Allah Ta'ala make this test a smooth and successful one Insha'Allah! AMEEN!