Interview tips for a situation

Background on my situation:

I was orientating on a unit. I was getting glowing reports from my orientator (#1) who I had been with every shift. I received a new orientator (#2) as my first one received the lead staff position. During my 6th week, I was pulled into the assistant manager's office and I was spoken to about my attitude specifically. This was a shock to me as I thought, for the most part, I was getting along very well with all the nurses on the floor and I had many nurses asking when was I getting off orientation and constantly chatting with me and it never seemed to be a problem. I did orientate with one nurse (#2) that we seemed to be struggling personality-wise and when I brought this up to the floor educator, I thought she didn't really respect what I said and pretty much told me to suck it up. I did this.

Ten days go by from week 6 and I am doing extremely well, or at least I thought I was. On the 10th day I am with ANOTHER orientator (#3). I am again pulled into the assistant manager's office to talk to again about my negative personality. After we had the first conversation about this, I had made more of an effort to not be negative, definitely be more positive and try to really connect with my orientator (#2) and keep putting my best foot forward. The weekend happens and again I am pulled into the manager's office on Monday morning. At this point I am pretty much days away from orientation. The manager's say that they do not think I am ready to get off orientation and they do not trust me to be alone with patients.

During the weeks I did my orientation, I have received non-stop glowing feedback from my patients. There was only one complaint and I actually had that patient again and the patient's family was looking forward to me being the nurse again. After much thought and contemplation throughout the day I had the last discussion with the assistant manager, I decided to leave my position, especially since they did not have faith I was ready to get off orientation and did not trust me with patients.

THE QUESTION

My question comes about as I start applying to other hospitals, how do I answer the question that will inevitably brought up why did you leave after X many weeks? And maybe were you terminated or did you leave?