Rename Days Until Derailment to "Safe Days"
With the current naming, even while on the green, that countdown timer still sounds like an impending derailment, doom and gloom.
If renamed to "Safe Days" or "Safe Days Accumulated" it would be a positive resource, and would be internalized as such. A great safety buffer with the focus on things done right and achievements completed already, not time running out until an inevitable relapse down the road.
Will Everett commented
I also oppose this idea. "3 days until derailment" doesn't sound impending to me at all. It sounds like it won't happen for a few days.
I'd vote against this, actually, although I do sympathize with the motivation. I don't want to be lulled into a sense of security. If I think I'm safe, I WILL lapse. I want to be reminded that I'm at risk, as unpleasant as that can be. If positive encouragement were enough incentive for me, I wouldn't need Beeminder in the first place.