Please if you can't manage this on your own, are beating yourself into a corner, get some help - you're not alone. I've been there. I got sober at 36, 38 now, it's never too early or too late to quit, just something your mind is trying to tell you. You can't write yourself off at 40, that's WAY too young!
We all feel at some stage as if we've 'lost it', are losing our minds, I've been in psychiatric wards a lot of times, never thought it would get any better - not for me anyhow. It was step by step but life now has vastly improved. I'm no better or worse than you, no special abilities, nothing magical about it, but I'm sober today.