I tried something from one of the books recommended on this site...it worked great to tame some of the tantrums...

Make 2 lines marked 1 thru 10.

On one line, label ways to handle anger/disappointment from quiet sadness (#1), to full blown tantrums at the 10 mark.

On the other line, label some common life problems from something like brother takes your toy(#1) to losing your home/someone you love (#10).

Now, discuss with the child some of their recent problems and where they fall on the problem line. Most will come out as a 1 or 2 level problem. Now, show the child their reactions on the second line. Most will come out a 9 or 10.

My son was shocked when he saw his emotions were so out of whack with his responses. Now, when the emotions start to flow, I ask him to rate his problem, and he automatically starts thinking about the level of reaction he should have. It sounds kind of crazy, but it's been working.

Can't remember what book it was in or I would give the author credit.