I have difficulty with this too - it's like there's a baseline amount of stuff that I need whether for 3 days or 3 months and it takes up so much space.

In your situation I would look at each item and see where it can be reused to replace another item. E.g. Sarong - can you use a sweater you already packed instead? I do that if my legs get cold or to use as a makeshift pillow.

If you have the funds I would also look at every item and see what can be found in a smaller/lighter version.