I also have this struggle. I have recently improved somewhat, but honestly I think it's because I started an anti-depressant. I had a baby 8 months ago too, and was depressed without really realizing it. So, make sure that is not the case for you. Sometimes it manifests in that feeling of being overwhelmed. My husband works alot too, and just being without any adult interaction brings me down at times. I am definitely a work in progress :)
But, what I am trying to do is this...
1. Choose my battles (I have a 3 year old that makes "strong-willed" seem like a huge understatement). I found myself correcting every little thing, and I'm trying to give him a little "space" to be himself. I was really nit-picking him, I think. That just made him rebel more. I try to save the real discipline for the times when he is outright defying me or doing something unsafe. I have had to except that little boys will be little boys though :) I know this one may not apply to you yet, but maybe down the road.
2. For tantrums, I used to try to talk him down or get upset, and that usually seemed to frustrate him more. I have started just ignoring him until he calms down, and so far, it's helping. He's a big talker and he hates when I don't talk to him...so I just started telling him that we can talk as soon as he calms down. I know he's older than yours are, but maybe if you show them early on that fits don't get them anywhere, it will help.
3. Sometimes I can re-direct him. Now that I know what sets him off, I try to look ahead and get him thinking about something else. We spend alot of time outside, because he loves that.
4. For extreme cases of frustration, I make sure they are in a safe place (crib, playpen, room) and I take a few minutes to regroup. It also helps to have some time away, so I would encourage you to get someone to keep the kids while you get out of the house. Even if it's for a short time, do something that makes you feel good.
Like I said, I am still working on it. You are not alone. Things have gotten better now that my son is old enough to spend the night with grandma! So every once in awhile, we get a break from each other. I end up missing him and all the chaos! Hang in there...it must be tough having twins!