If you want to go to Florida by car, you must plan to drive awhile.
 
 
 
Continue
 
 
 
 
  The period after "awhile" signals to the brain that it has come to the end
of a main clause. Because the "if" clause" is adverbial to "must drive,"
it is now, if it has not already been, chunked to it.
If you want to go to Florida by car, you must plan to drive awhile.
 
 (c) 1997 Rose Parisella Productions