Even the 'no mercy' option is pretty lenient. I've got it in the back of my head that we should make use of the auto-ratchet number of 'max safe days' when recommitting. (i.e. use the minimum of current-practice and max-safe)
Another way of reducing the number of days off that you actually get is to measure the same IRL goal from different angles. e.g. for writing it might be word count and writing time. When one derails, the other doesn't necessarily go with it.
Aside: @drmaciver's comments had to do with the old design, so this particular setting has moved to the 'commitment' tab.