vibrato is so hard

my vibrato is VERY TENSE. in theory I know everybody says just relax your hand or wrist...but my hand gets tense after 3 seconds!! and the sound gets ugly
I want to break my arm!! !****!...

I'm not a violinist, but the attitude that produces a remark such as

I want to break my arm!! !****!

would seem to me counterproductive. Vibrato is an expressive device, and although there are, of course, technical considerations, ultimately you just have to feel it--or at least that's my approach on the cello and guitar. It's difficult for me to believe someone tensing is really at one with the music. I'd recommend putting the instrument down for a while and coming back when you're refreshed.

While I am not a violinist, I have done considerable work with several string players, and have learned some techniques for coaxing the best sound out of a string instrument. One of these may be helpful:

Vibrato cannot be forced. You are probably clenching the neck of the violin and tightening your hands quite a bit while playing. Instead, try holding the neck loosely and barely touching the strings while you play. Then, instead of making your fingers rock back and forth, try using your arm and your wrist. See if you can feel the swaying in your whole body.

If this still creates a horrible tone, play with straight tone until you can consult a professional. Watching professionals play can also help: I would suggest watching (or listening to) Jascha Heifetz, because of his physically expressive vibrato.

thank you "egretboy".
your writing is worth reading.
unlike the first one (must be a canadian...)