The lighter your backpack the easier and maybe more pleasurable the walk.
A lighter backpack implies carrying only what is absolutely essential and ensuring that what you do carry is the lightest of its kind.
For something to be essential it must contribute to your safety or health. If it doesn't then don't pack it. For instance, if you're a bloke, a shaver fits neither
category, so allow your beard to grow. If you're female, make-up doesn't fit either category either - leave it behind.
Carrying the lightest of everything can be expensive. To protect ourselves from the rain we carried heavy duty ex-military waterproof ponchos which cost £20. They weighed a massive four and a half pounds! We have 'waterproof' jackets, however we doubted their ability to keep us dry in a torrential downpour. The lightweight alternative would have been to get ourselves Gortex technical hiking jackets. They weigh just ounces and would have kept us absolutely dry. They'd also have cost upwards of £170 each.