I love AJ's "customization" of PPP--or maybe "Personalization" to add another P. And that there is no Perfect in PPP.
What was most helpful to me was to use the PPP as a guide to avoiding repeated errors that were barriers to getting where I wanted to be with my wardrobe. I was imPatient enough that I rushed into some things I didn't really need and then might not have the chance to get something I did. I was imPractical at times in accumulating things for my imaginary life. I wasn't Picky enough when my little inner voice told me the shoes really rubbed a little, the size wasn't right, etc so then I would later be unhappy with the item.
All those things are true and good reasons for PPP but not the same as making a reasonable choice.
Now, one thing I use as a guide, if I want to "fill a hole", or even if I just happen upon something, is whether once I got said item, will I say, that's that for this (season, year) or will I still be looking the next day or week. That's a red flag to me that I shouldn't go for immediate gratification, as it'll be too short-lived. Because one area of wardrobe disenchantment I wanted to improve upon was not spending a lot of time wishing I had something else almost just like what I just bought. Goals, or lists, and planning, yes... but overall having a greater sense of satisfaction and enjoyment-use with whatever it is I bring home.
So PPP also helped me reallze not everything that seemed like a hole, was a hole, and that leaving some of these things open made room for even more fun or something unexpected to show up.
I wanted some "summer" oxfords for work , but because I wear conservative items and darker colors on bottom and not, say, jeans or white jeans, I didn't want super-playful ones. So it was kind of an imaginary shoe that would look lighter but still classic. Plus it has to be super-comfortable. I've tried over a dozen and still haven't hit it, but really, it's because nothing was really close enough that I could see wearing regularly. There wasn't one yet that really "made" my outfits work and also fit well. So it's not just that I'm a picky saint, it's practical. But it's also been a good learning experience--fashion research--because I've learned a lot about what shapes, colors, contrasts look best and I'm more focused on what would work, if I find it, or what other type might work for fall or winter, if that shows up. So I decided it was not really a "hole" that had to be filled--leaving it open leaves me the pleasure of perhaps something I haven't yet come across or imagined.
The parallel with your sandal hunt may be that, if you can immediately see yourself in a number of happy-fab outfits with that sandal, and you don't feel like you have to have another one right away to replace these (not saying you can't buy another sandal if you find one--just using the most stringent guidepost which is the pleasure of no longer feeling pressure to find the same thing, so we can be on Team enjoy more and shop less), it seems like a good choice.