It would seem getting rid of the negative motivator completely could be impossible in such situations, short of delusion or intentional forgetfulness/detachment.

You need to remember that positive and negative motivation are managed by distinct brain subsystems. You can have a positive preference for something, without also having a negative preference for the lack of it.

For example, I can have a strong preference for health, without being in constant fear of getting sick.

It's also true, for instance, that failure to look both ways when you cross the street carries a "significant non-bogus threat", but for a normal person, this doesn't induce any negative motivation.

In short, removing the negative motivation is not the same as eliminating your preference -- the two motivational systems have a fairly high degree of redundancy.