OK, this is just my opinion, so here goes.
First, I adjust the contents of my pack to fit the area where I'm going. There is a big difference between surviving a night in the low desert where it is very dry, only gets down to the low 50's, and fire wood is abundant and doing same in an above timber line area with a storm coming in.
Second, I leave everything out that I'm not sure I'll need. Why ? Because if you get into this "I'll take it just in case" attitude, you are going to be packing all sorts of stuff. That can lead to an attitude of leaving the whole pack behind instead of just taking a few things you must have.
Lastly, I like to take stuff that will do double duty. Clothing is a good example. A warm cap or baclava. Gloves even though you may not need them. A extra warm fleece top. Synthetic, fast drying base layers that stay dry by allowing moisture to pass through it. And, above all, a first class shell.
Lastly, be aware of where you are, what the weather is doing and what you need to do to stay safe. You can do much better if you get down into the timber rather than let nightfall find you on an exposed ridge with the wind kicking up. Start preparing to spend the night, or simply add clothing before you chill or get wet from the rain. And before it gets dark.
I'm indebted to guys like Okanagan for showing me a few simple tricks. A thin foam pad, like a cut down, 5/16th's inch ensolite pad isn't a 2-3 inch mattress, but it is far lighter and more compact. It will keep the cold out. A nylon tarp or a light bivy sack in a semi sheltered grove of trees, or rocks, can be alot more comfortable than you'd think. Put all of your extra clothing on, and use his secret weapon - 7 hr., tear open chemical hand warmers. If you brought some extra food and have a water supply, you will be fine. If you can build a fire, so much the better. Make it 5-6 feet long and stock lots of wood before you turn in.
My last suggestion, is try all of this out when the weather is nice and see how well it works for you. You may want to adjust the basics a bit.
The bottom line is, you don't need much. If you plan well, pick stuff that can do double duty, and use your head, it works.
Heck, just going to the trouble of finding a thick grove of trees, in lee of some natural feature and you are a long way to spending the night dry and warm. E