It is from this video. It is at around 4 minute and 54 second. Here it goes:
Curiosity motivates you to ask questions and learn: What turns you on? What turns you off? Is it ok? How can I make it better? (Because) you don't assume that you have figured it out and you know until the end of time how you or the other person or the dynamic between you is going to be.
It seems to me that without the word because the last sentence doesn't make sense. How can someone know what the dynamic between them is going to be if they don't think they figured it out?