I have also been feeling this increasing frustration level in the last couple months or so. In my case it is because I am in a local community college orchestra (I'm not a student there, just a community member), and the pressure there is phenomenal!
This conductor knows what she's doing, and should actually be commended for preparing college students for the real world (read: professional orchestras) but she tends to be a bit lacking in positive feedback. This is my 3rd year with this group, and the constant "This is still way below tempo", "It's too draggy", "Don't rush me!" and "Look at my stick at the end of this phrase!", whether said to my section or other sections, is very discouraging. In other words, improvements are not commented upon, until they are up to her standards.
I've therefore started to honestly believe that no matter how much I practise, it still won't be good enough! Now, it's great training for keeping a good attitude in the face of adversity and all that. However, matters came to a head last week when I literally could not practise! Not only the orchestra music, but anything! I just cuddled my violin for 45 min. or so.
My solution? I have recently found a local Scottish Fiddling club, have been to 2 meetings and really enjoy it. The change in genre from classical to fiddling is very refreshing; add to that there is no criticism whatsoever - if we get it, fine, if not, fine. We are there to learn tunes and have a good time. I can see that this could lead to laziness, bad habits, lowered standards etc., but as a contrast to the previous conductor's behaviour, it's the best thing for me.
You might want to try finding a different situation like this - something that's still violin-oriented, but that is different enough to break the obsession & get you back to the fun!
Hope this helps!
Laurel