I think you've hit everything right on the nose. That's what I was trying to get at. Two grown adults shouldn't have to worry about "protecting" one another. If things are not working out, I agree to get it out in the open. There is no sense in trying to solve a problem if it's not met with the same understanding from both parties.
Let's say you and I working doing an oil change on a car, but we didn't tell each other. I may start to do a transmission fluid change, and you do an oil change, then we have a big mess. NOTE: I am not a car guy at all...so if this analogy in real life would not end up in a big mess, but rather a blissful situation where two objectives were completed at once with no incident, then I appologize.