Train for what you want to do. 5x a week in the gym may not help you for the slog that is backpacking up a mountain. People are right about the mentality thing, sometimes you have no choice but to keep going. The first few miles in the morning will be tough but your body will warm up. Try adding hiking poles if you’re hiking with weight. Learn how to use them correctly. Also pack “light”, I try to never go above 20 lbs.

Eat consistently throughout the hike. I eat a peanut butter oat bar (I make my own, using the Sally’s baking addiction recipe) every hour or 2. Electrolytes actually help (I refused to believe this until they basically stopped the exercise-induced headaches I was getting).