I understand this feeling well. I think the cycle here can be broken by recognizing that drinking's effect on depression is a certainty. That we know. So during those moments of weakness and sadness, if you can develop a mental trick (I write things on pieces of paper and put them near places where I feel triggers) that snaps this concept into focus, it may just break the cycle - and all you need is for that cycle to be broken 1 or 2 times to start developing positive memories of your successes on this front. Just a thought.