Fiscal discipline is a word generally used for the financial discipline of the government sector, spreading into multi-years so that pre-defined goals are achieved / at least to some extent. In a broader view, if the author, applies the word to the individual, it can be for achieving a major project in his/her life. Major projects for a common man would be: Study in Abroad for self or for his kith and kin, construction of a bungalow, performing marriage to children in a prestigious manner, etc.
To a draw a line between the expenditure and fiscal discipline:
One should list out all the requirements he wants to have. From that list, he should eliminate the things first whatever he can eliminate. At this point once again he will have to prioritise the things of requirement. so that some other things would be eliminated. Then he should finalise the things of immediate requirement. At this point he has to check his pocket and he has to re-check whether his pocket would support the list finally arrived at. If not, still he can eliminate the things which can be postponed to some extent even though it is of immediate requirement. Like wise one can draw a line between expenditure and financial discipline.
Here I would like to quote that for the sake of society and to have a certain dignity of a kind a person want to have, have to be spendthrift and cannot a draw a line between expenditure and financial discipline. I mean to say one has to be wise and flexible in making expenditure.