How do you come back from a relapse

I just got out of the hospital after ODing on benzos last night. I lost someone very close to me and relapsed after 3 years sober. I'm potentially staring down the rest of my life without this person and I don't know if I can handle that. My high school girlfriend overdosed on heroin when she was 19, I've had one marriage annulled, and lost both parents by the time I was 26. I'm 31 now and this feels somehow worse than all those things combined. Maybe it's a mix of my age, and the overall decline and depravity of the Western world, but I'm at a point now where I don't see any real reason in not just being a junkie again until inevitably OD. How do you bring yourself back from this? The first days are usually the hardest after a relapse because you are still addicted. But im not, I was sober and don't have cravings. This just feels more existential.