On a 9-day trip to Germany, I brought one carry-on and a personal item (backpack).  Even though I packed light, there were still multiple items I didn’t even touch.  I usually bring one or two extra shirts because they’re lightweight and if you dump coffee all down the front of one (which TBH is a real concern of mine), I want to ensure I’m prepared.  Of course, pants are another story. I only bring two pairs of pants.  So if I stain them, it’s tough luck for me!  I ended up wearing the same few pieces over and over again, which is the idea.