I know how you feel. My first appointment with my new therapist this last August was difficult. I told her about the suicide pills I had hidden away "just in case" and she wouldn't let me leave her office until I promised to dispose of them, tell one other person about them (my sister) and then email her when I had done that. Then I had to come in the next day for a follow-up.
I didn't want to get sent to the hospital, so I did as she requested. Afterward, my anxiety levels were so high that I actually sewed my razor blade to my arm. I don't know how it happened. One moment I was contemplating my embroidery kit and the next thing I knew...I'd done it. It was rather horrifying, but I felt much safer somehow.

My point is, when you're asked to give up something that is your life-line, even if it appears to be harmful on the outside, it can cause enormous levels of anxiety because you simply aren't prepared to cope with such changes.

Two days isn't that long, but it can feel like an eternity, I know. Here's what you can do: make a hour count of the day in a notebook and every hour you go without self harming, mark it down in the book. This way, you will be able to see your progress and focus on the goal. If you need to self harm, make sure you write down your distinctive feelings around the time you did do it, then try to get right back on track. Take it hour by hour.

You can do it! I believe in you!