There seems to be something missing grammatically from this. But it still contains the sense that the person is not making any assumptions about the future. That is, there is enough uncertainty about the future, that the person is not making any projections about his/her future. => Not making any plans, because can't tell how current situation/circumstances will progress.
Things containing this 'one day at a time' phrase often mean something like this. Not looking too far ahead.
Is the person a prisoner or something? Or accused of a crime? Without the context, can't tell what is going on with the 'at judge' thing.