In my case, I took an OD of a substance I won't name but it was a strong prescription medication which I had stockpiled. I knew I wanted to take the overdose and I didn't need to think twice. Around 15 minutes after ingestion my heart started to race and I was in and out of consciousness up by a quiet walkway where there were very few people around.
Despite knowing I didn't want to live, in the moment it's also quite terrifying knowing or at least in my case, thinking, I was about to die.
A passer by found me and called for an ambulance and I was taken to the hospital. I could not walk and I couldn't speak as the medication shut down my central nervous system. I blacked out in the ambulance and woke up in a recovery ward the following morning. A psychiatrist assessed me and told me to go home. I don't regret doing it, but each time I was made to feel like an idiot by mental health professionals.
I've tried this method three times in total, taking higher doses each time, but always had the same result so I gave up trying that way.