If you dream that you are carrying a knapsack or backpack, it can be a sign that you are carrying an emotional burden in waking life.
Struggling under the weight of a heavy knapsack in a dream can mean that you are having trouble coping with difficult emotions.
A knapsack is used to store supplies that will get you through a difficult journey safely, so a knapsack in a dream can represent the resources that you have to get your through difficult times. Your dreaming mind is reminding you that you have the skills to overcome and obstacle that you have encountered.
If you dream that you are carrying an empty knapsack, it can mean that you feel unprepared.
Some people who believe in reincarnation think that a knapsack in a dream holds the things you have taken with you from a previous life.