If you don't believe you can stay sober, you won't. I'm convinced of that. I'm equally convinced that believing you can stay sober is no guarantee that you will. Our minds are tricky, and prone to lying to us at times.
So for me, I will do the work in the quiet and confident belief that I will remain sober. If I start debating it, I am that much closer to another unnecessary (and dangerous, potentially fatal) test run.