That's what you needed. It gets easier the more you do it.

Next time she asks, "Can I look at your bank statement?" answer back, "I'll have to think about that." Then you can let her, but at least you practiced pausing and not making acquiescence a reflexive response.

When you're at the breakfast table, and your wife says, "Pass the butter." hold off a moment or two. Take another bite of toast before you fulfill her request. That behavior in most people other than you would be passive/aggressive. In your case, it's a convenient way to build up those mental muscles of self-ownership.