Problem face while Answering, Why Did You Leave your job during second Interviews?

I have given information to my company. I had worked with them for four continuous years. My boss was really very harsh day by day it was becoming difficult to handle him. I was not able to go for any interview since my office time was so hectic. Hence I decided to leave the job.

Is it the right way to answer? Certainly this will never work. No body would accept it. This was told by one of the jobseeker who was really confused with the question and went on to speak the bitter truth. However I must add that he failed to win the heart of recruiter. I must add that this is really a confusing question and you should be diplomatic while answering it. For you sake I am writing what the jobseeker could have told to get the job.

1. He asked one of the managers after failing in the interview, "I don't want to walk into an interview and be negative about my boss and the situation I was in, because I can definitely handle a lot but what your suggestion about it is.
   
2. The manager replied, "I would go with something like" after four years I feel like, I want to take new challenges and I want to take sometime to really focus on something which I love. It's vague but it's reasonable and the recruiter will really agree with you because it's not one year but four years and they would have also gone through similar position.
   
3. It really can be true that your boss might be a micromanager, your coworkers might not be good or the environment might be toxic. Yes we all know that this can really happen. In fact this is in the minds of every recruiter. But you can really not tell that. You will really be a sufferer if you tell the truth. In fact this makes the recruiters think that are you really very tough to handle or was your boss really a micromanager. This will create a chaos in the minds of recruiters. However you can avoid this and tell some different story.
   
4. For example you can tell the recruiters that you want to face new challenges. However you might think that it's really unfair that you cannot tell that your boss is crazy which actually the case is. However I recommend you that never fall in any problems. You will be required to give many answers after this. Recruiters used to contact your previous employers and they might be against you. Anyways try to avoid all this and give some diplomatic answer. 

Think from brain and not from heart and I hope you will be able to tackle the problem.