There's a difference between realizing that you're playing for money and allowing yourself to let the money impact your play. So the thing to try to avoid is playing with amounts on the table that might cause you to consider different actions. This is especially true in cash games where you can always reload, so if you're hesitant to risk your stack when you think your favored - and not necessarily even a big favorite - then you're probably out of your comfort zone and should play lower.
One somewhat tricky thing - for me anyway - is that my comfort zone isn't always the same level, so I have to figure our what it is at any given time, although I can start from where it usually is as a guide.