Why It's Impossible to Memorize Anything Ever

So I'm studying the skin chapter in Step Up to Medicine, and I get to the disorder called lichen planus.  No big deal, the book tells me just to remember the 4 P's: pruritic, polygonal, purple, flat-topped papules.  I can forgive them for the last one (I can call it papule (comma) flat-topped, like a last name (comma) first name sort of thing). 

But now fast-forward two pages later (aka three facebook breaks and two youtube videos later), and I get to basal cell carcinoma.  OK, no biggy, the book says it's classic appearance can easily be remembered by the 3 P's: pearly, pink, papule.

. . . .

I'm sorry but that is too many P's in too short a time!  How am I supposed to remember which are the 4 P's and which are the 3 P's, and which one goes with which?  Where is the mnemonic for that??