Ever since reading The Secret a couple years ago, I've made it a habit of always thinking about what I want instead of what I don't want, or turning a negative statement into a positive statement.
This has filtered down into my parenting technique as well. I'd read somewhere that if you tell a child, for example, "Please don't climb on the bookshelf." The only thing the child hears is "Climb on the bookshelf." and that's one of the primary reasons kids misbehave. They need to be told what to do, as opposed to what not to do.
So I've been practicing and catching myself when I tell Aidan not to do something. I turn it around right away and tell him what I want him to do and sometimes I have to stop and think about it. I've been so accustomed to expressing what I don't want that it can be difficult sometimes to think about what I want instead. If I don't want my child to stomp around on the floor (we have neighbors one floor below us) then what do I tell him I do want? To walk softly please. If I don't want Aidan to put the holly berry he picked in his mouth, what do I tell him? "Don't put that in your mouth?" I used to say that. I now say, "Keep the berry in your fingers." or "Hold on to it."
Having a child to practice positive statements on is great. You have to really stop and think sometimes about what it is you want when it's so easy to think about what you don't want. I'm sure that at some point it will be as easy to express my wants as it is my don't wants. :)