How do you decide which is which?
FI and I have one, joint account and a savings account. Per your recommendations a long long time ago we've been thinking about doing 2 separate accounts to use as our personal "slush" funds.... we haven't done it yet though and I think a big reason is because we can't agree what would be considered joint purchases or personal ones (mainly mine). One example would be decorative items... FI could care less and they aren't necessary. I'm a freak about interior decorating so that's me personally, is his argument. Mine is that it's for the household, it's something we will all enjoy/use so it shouldn't come out of my slush fund just because he doesn't really care about it.
How do you handle this type of situation?
ETA: IMO personal accounts should be for outings, like guys night/girls night or things specifically for yourself like clothes, xbox games, books, specific movies only one of you want, etc. So literally personal "fun" stuff.