My first CTB attempt (Many years ago) I had the pills in my hand and I just had to shove them into my mouth. I was shit scared of what I was doing. I stopped myself.
It was my will to live, scared of dying of what I was about to go through. Our human instinct to live. That's what stopped me on my many attempts. After one of my attempts, I wanted to live and went to counseling and found myself in a psych hospital (Luckily, the food served there was awesome due to being a university hospital).
If I wanted to CTB now for my current reasons, I would have done it. For reasons, I think it's my unconsciousness that is trying to give myself a chance to live. I have some methods planned and waiting for supplies to arrive.