Yea I doubt you could be 100% of yourself in a dream because your mind is doing other things to create the dream. Besides, you are sleeping after all. With that said there are ways around it. Your memory and logic didn't disappear, its just not working 100%. Like the example you gave, I bet you have forgot to do it just as many times.

The most common thing to do is just keep repeating what you want to yourself. You have to really get it stuck in your head, when you notice your dreaming do x. Thats how RC's work. You do them all day so when your dreaming and can't remeber much you do it anyway.