I have a feeling a lot of people have those days, myself included. I was talking to a few luthiers and professionals about it and apparently, the violin itself can sometimes be responsible. The weather conditions can have an effect of the sound of your violin as well as the room you play in. So, don’t worry! It’s not just you!
I am beginner, and initially had a tendency to “blame” my instrument, etc. for everything that went wrong. I was rosining the daylights out of my bow, for example….Then after sticking with it for at least 3 months and feeling I was ready to make a commitment, bought a nicer instrument. It sounds great when my teacher plays it so now I can be reassured that a lot of my bad sounds are growing pains.