Not testing the food
Crabs will deliver you energy
Bonking
Avoid taking silly steps. When you are approaching a longer route, always feed yourself well, as without that, you may make it to the top, but descending will become problematic.
Overhydration
Let's break the typical thought that drinking more is beneficial for health. It's never like that, as taking too much sodium will cause delusional hyponatremia, which can be fatal sometimes.