I have to say I still don't see how one can practise mindfulness on winter roads. Good on you for realising a dangerous situation and being strong enough to say no. Of course you are anxious, but being anxious at home has got to be better than driving on icy roads being anxious on every corner and possibly having an accident. Hopefully your boss realises you were only being sensible; he probably should not have asked you to come in on a day like this anyway.

Forget mindfulness for now ... just practise some relaxation and calming. You did right.