How do you decide what potions to keep?

When you hit ascension 11 the game takes away one of your potion slots. This means if you don't have potion belt, you can only have two potions at any time

consumables were a big part of old roguelikes, though some newer ones don't use them at all. StS includes them but then gives you a tiny inventory? Doesn't make sense. Especially if you want to combo potions together like flex and ancient. I notice the limited inventory is also in the sequel. There was a time I even had to skip fruit juice near the end of a run

if you overflow your inventory, do you tend to keep things like fairy in a bottle and 12 block potion? Or what's your criteria?