Forgetting an essential item can cast a negative cloud over a backpacking trip. Make sure this does not happen by consulting a backpacking gear list before you leave.
To avoid leaving an essential backpacking item behind, consult a list as you gather your gear and food before the trip.
The one I always refer to is published by backpackinglight.com.
Try to never leave without consulting this list. It likely takes a few minutes to make sure you have all your essential gear, and enables you to avoid the bummer of finding you have forgotten something, miles from the trailhead.
Twice I have left my cooking pots in my dishwasher in the last few years. The first time I realized this before I got to the trailhead, and was able to pick one up at a corner store between in Garfield, Colorado (West of Monarch Pass).
The second time I was setting up camp after hiking in, and realized my pot was missing. I had no choice but to hike down the next morning and buy another one.
It pays to be extremely efficient and organized when loading your backpack. It is a balancing act, to not take more than you need, and not leave anything out you will need. That is were the list helps.
One thing that helps me a lot is to store all my gear in one location to dry out at home. When I am ready to prepare for the next trip, I just have to collect my gear from that one spot, and not have to look all over the house to find my gear.
The real essential items for me (besides the cooking pot), are sunglasses, bug spray in the summer time, my tent and sleeping bag, rain gear, my trekking poles, sun tan lotion, and of course my cooking stove and fuel and a bic lighter. (I keep waterproof matches as a backup for my lighter.)
In the summer time I only load a thick polarfleece sweater for warmth. That and my rain gear tends to take the edge off of cool mornings and bad weather.
Other items I always make sure to load are a collapsible 5 gallon water bucket, (so that I can camp further from water), and a waterproof sleeping bag cover. The sleeping bag cover ensures I will always be have a dry bag, even if my wet dogs are snuggled up against me.
The snow is melted off of most of the passes now, so get out and enjoy the high country. Fall will be here soon enough. Consult a list before you go.
Me and the dogs are headed out tomorrow, for almost a week. Yeehah.