When I was first diagnosed, I was focused on cure. I took two clinical trials, plus two rounds of chemotherapy. However, when the cancer came back a year after my initial treatment, I was told I couldn't be cured. I decided to take control, and procured a drug that is sitting in my fridge. Every now and then I take it out and have a look.

When the time comes, I will draw the line for myself. I want to be quite present, propped up in bed, having a conversation with people. I want someone to hold my hand.

There are five friends who want to be there. Over time people have opted in, opted out, and I'm just getting consistency in terms of people committing. Their being present in a room is not considered aiding and abetting, but I will need to be well enough to get the drug from the fridge, go back up the stairs and have the presence of mind to measure it out. Well enough – and brave enough.

I've drawn the line.

I'm assuming that because the cancer is in my liver, I will see my body filling up with fluid. My ankles will swell, my face will go yellow. That's my line. But I can't know the order of events. I have had days where I've thought: "Right, today's the day, I can't bloody stand it." But it's not really the day. Maybe I will pass the line and miss it. Maybe I have to bring the line closer.

It would be nicer to be iller and to submit to the help of people, but I can't put anyone in that position. I have to be emotionally and physically well enough to follow through – to take a very, very difficult decision, but one I passionately believe I should have a choice over. I hope I live to see the passage of Lord Falconer's bill to legalise assisted dying, but I doubt I will. I have very little time left.

I don't break the law – I'm not that sort of person. On top of everything else, you have to deal with your anxiety about doing it. Yet I did give money to a stranger for a drug that may or may not be what it says it is. I was terrified it wouldn't arrive or would be blocked at customs. I've had it in the fridge for over a year now.

It's hard, but I have to think about taking the drug. I've been assured that if you take the drug and then a bit of alcohol or chocolate – because the drug is very bitter – you will fall asleep and die. And that's all I want. I don't want to end up incapacitated, taken to the commode, turned in my bed, out of my mind, unrecognisable to myself.

I can understand people wanting to go down the palliative-care route. There is some part of me that thinks, "Oh, just submit to the care. Just allow yourself to submit to it." (This is the route I'm going down at the moment.) They will take care of you. And I'm sure that people who are ill want the system to take care of them. But no one can guarantee I will have a good death. I've been told that the likelihood is I will need 24-hour care, probably sleeping for most of the time. I can see that some people might like that. And maybe, if I start taking morphine and drifting off anyway, that might be OK for me too. But I want to have the choice.

I went overboard. I also bought powder from China. It was terrifying to me, the handling of it. I had to cut the Mylar bag, to measure it. It was so pungent. I was getting confused about grams. There's a sort of dust that flies out of a powder. When I got it in the bottle and managed to put it in the fridge, I thought, thank God for that.

I told everybody the drugs were in the fridge. One of my sisters was very resistant to the idea. She hated it, understandably. She became anxious I was going to take my life at any point. I am the youngest of three girls. My middle sister is almost eight years older than me. She was very protective of me from the beginning. But the luxury of having a terminal illness that happens over months is that you can bring people along over time. She has seen me get increasingly ill and is much more an advocate of assisted dying than she was. She certainly doesn't want me to suffer. Nor do my parents.

Permission is a big part of this. I am constantly looking for permission. "Is this OK? I'm going to go." I've been told a lot of people die when their loved ones leave the room. People say: "You can go now," which suggests that when you're in this place that I'm in, you want people who are alive to give you permission to go. Which, of course, is very hard to do.

I feel I'm living very well at the moment because I'm thinking about a good death. I'm having real communication with people. And it's because I'm connected to people that I feel I can live.

The crazy thing is, I've written about what I'm doing, some friends are making a film of me, and some part of me feels that when I'm dead I can find my way back to myself. That's so illogical, but the thought is giving me comfort. I will be in the public domain. It will be easier to find me. All these crazy things we think about when we don't know where we're going.

The idea of losing yourself, losing your consciousness, is huge. I'm terrified of losing the person I am. I've got to leave little markers for me to find my way back.

As told to Paula Cocozza

• This article was amended on 14 July 2014 to remove some phrases inconsistent with Guardian guidelines on reporting issues concerning suicide. The Samaritans' 24-hour helpline is 08457 909090.