Each person is, of course, an individual with an individual experience of depression. As you’ve found, you can have periods without the struggle. I’m very sorry that you are struggling now. Please, fight the temptation to go back to addiction as a response.
A far more healthy way to manage your current situation is to go back to therapy. Therapy for major depression is rarely a one and done situation. You need and deserve to have intermittent support as well as reminders about how best to use your own inner core of strength to help you through.
I also urge you to participate in one of the forums here at PsychCentral. Go to the “Find Help” tab and click on forums. The forums provide a place for people who are dealing with similar issues to give each other advice, encouragement and general support. Visiting regularly will give you a community of people who are there for each other.
I wish you well.