As a mum of one who has just come out the other side of the terrible 3's, I can say this will pass. I could have and most probably did write more than one post very similar to this regarding DS's behaviour. We cut down on food additives and preservatives and it seemed to make a small difference. The main thing though was just time. One day our sweet little boy just reappeared better than ever. We made sure we didn't give in to his tantrums, used consistent punishment wherever possible and offered lots of cuddles. There would be a point where a tantrum turned from wanting his way or whatever to being genuinely upset, this is the point that we offered cuddles and it usually worked to end it, sometimes even with happy co-operation . I saw something after he started improving that made so much sense. It was a picture of a spiral (like a cyclone or tornado) and on one side it had "disequalibrium" and the other side was "equalibrium". Each year of age was one turn of the spiral with the half years hitting on "disequalibrium". I'm not sure if that makes sense, if I can find the picture I'll post it. It really struck a chord with me. I wish I had seen it while DS was going through it. I'm not looking forward to the next round.

What I did to cope -
I hid in my bedroom and screamed into my pillow on occasion.
Distraction.
DS started doing more complex puzzles (24pieces) which was more challenging for him than the wooden ones.
Asking for his help. Anything that could be considered helping whether it actually helps or not. EG sorting the washing. I'd have to resort it after DS helped but it made him happy to help.
Don't forget to praise the good things.
Time out for myself. DH works stupid hours and was often sleeping but I went to the gym class once a week for an hour on a saturday morning. I had to take them to the creche sometimes if DH wasn't home from work in time but I made sure I did it every week. I need to start going again, DD's hitting the terrible 2's
When all else fails - ABC 4 kids for DS and stiff drink for me


And as LL said, pick your battles. Eg you get the red shirt out, she wants the blue. It doesn't matter. Let her wear blue. Not only that - anticipate them. EG without fail, DS wants a different type of pasta to the one we've cooked. Solution - ask him first. Seems silly but it makes him happy. So if you know there is something that will set her off, change the routine so she has some input.