1) If you spend too much time looking off at the view instead of at where to place your feet, you will soon fall. (Corollary: If you don't look up once in a while, you might as well not be there.)
2) Every downhill has to be paid for with an uphill. The uphill will tend to be steeper and longer than the downhill.
3) If you prepare for bad weather, it might not happen. If you do not prepare for bad weather, it will definitely happen.
4) Always be prepared to share your food or water or gear. Then you will not have to feel guilty as someone else shares freely, when you need something.