What size you wear? I wear 10's, let's see if you can fit your feet
He’s just saying that not everyone has the same ‘shoe size’. He uses that metaphorically. He really means not everyone has the same life, and it would be hard for someone to adapt to some new sort of lifestyle. Like, if you wear size 9 shoes and have to trade shoes with someone size 5, it would be hard to adapt to.
“Let’s see if you can fit your feet” He’s meaning that lets see if you can handle what he’s been through & see if you could fit it.
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