How can I overcome my existential depression?

I'm an agnostic deist and an absurdist so I ign life meaning- I also doubt an afterlife exists. I'm a realistic thinker and the other night a thought struck me that was rather detrimental to my psychological health which has been waning over the past year and a half. I was very drunk and considering the state in which I wanted to die; the intrusive thought, as depressing as it was, was impossible to ignore. I couldn't help wondering whether since my death probably lacked any cosmological significance, and humans by their very nature are selfish pleasure driven beings, that since I was feeling merry at the time, death wouldn't bother me if it struck at that moment. The truth is, I would have been perfectly happy dying in that state- I think that's sad. I have become apathetic and lost in the meaninglessness( or self igned meaningfulness) of reality and I have lost motivation and reason to do that which I once loved. What must I do to conquer this insuperable stupor that I have become enthralled in?