def break_up_lines(text, max_line_width=80):
    """Break up the text in the given string so no line is longer than
    `max_line_width`. Any existing line endings are left unchanged.
    
    If any containing word is longer than this line width, then it will
    be broken up in order to meet the line width restrictions. A "word"
    means any consecutive string of characters not separated by whitespace.
    
    @param text {str} The string in which to break up words.
    @param max_line_width {int} The maximum line width allowed. Default is 80.
    """
    import textwrap
    lines = []
    for line in text.split('\n'):
        if not line:
            lines.append(line)
        else:
            lines += textwrap.wrap(line, max_line_width)
    return '\n'.join(lines)
