Plan is useless but planning is useful
Things are never going according to plan in chaotic environments (which is most real-life environments).
But, planning forces you:
- to know your SWOT (strength, weakness, opportunities, and threats)
- to know what your values and principles are
- to see possible common exceptions
- to make contingency plans for these exceptions
- to prepare for the worst
Hope for the best, prepare for the worst, expect the most likely.