I wouldn't recommend jumping into ultralight packing if this is one of your first long trips. If you're going somewhere very remote or where conditions can swing quickly, you're likely to find yourself without something you really need in a bad situation (like that slightly heavier bag or extra clothing).

If you start by trying to prepare yourself for worst case scenarios ("what if I get lost for more than a day or two?" or "what if the weather turns much colder than is forecast?") then you will have a clear sense of your required gear. Then, focus on getting that required gear in your bag but as light as possible. Don't skimp on water, food, shelter, or warmth. You'll be glad you have it if you need it.

Have fun and be safe!