gomubukai, I think everyone has days when it is harder to make themselves practice than other days.  I know that I do.  But if you want to improve on the instrument, you know that it is something you have to do.

You hear here from some folks who stopped for a while and then took the instrument back up.  But from what I have seen with playing music on various instruments for quite a few years, most do not.  The people that come back to an instrument after giving up on it or "taking a break" are the few, not the many.  Still, it is always possible you might beat those odds.  But knowing the odds is part of why I myself avoid such breaks in practice.

That being said, I would have a few questions.

1.) What is your current practice routine or schedule?  What are you supposed to be doing when you practice?  Is it a schedule/routine that was given by your teacher or are they aware of what you are currently doing in practice? 

A common problem I have heard of with practice is students being told "Practice!", but not being told how to go about it so far as how much time on what exercises and etc.  Perhaps you and your teacher need to review what you are doing in practice and talk about some possible ways to get it to work better.

2.) Is practice the only time you play the instrument?   If you never pick it up just to play for the fun and joy of it, to enjoy making sound, then practice sessions can get to feeling like a lot of work for no benefit.  "All work and no play" is very hard way to try and learn anything.

3.) Is the genre of music that you want to play what you are currently learning in lessons?  It can make things seem pointless and hard to be enthusiastic about learning if you are for some reason studying repertoire that you actually have little or no interest in being able to play.  Yes, many of the basics are still the same.  But that does not make it seem any more enjoyable.

To give a quote by Albert Einstein that comes to mind..

'Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.'

I don't know offhand, Oliver.  Probably someone has figured out the statistics on it somewhere. 

Doing a quick search, I found this:

http://www.essortment.com/popu.....40020.html

But I'm not sure if those are the absolute most popular.   All mentioned quite often, though.

I think there likely is also a difference between if one is learning in the school system or from a private teacher. 

There sure seem to be an awful lot of methods/schools for violin teaching.

I think the matter is probably further complicated by a lot of teachers using more than one book/method in their approach, so there are quite a few "hybrid" schools/methods out there too.