I suspect your daughter is a whole lot like you. I find that the children with whom I get really emotional are the ones who act like me, so when we clash, they hit "all my buttons".
It's hard not to react emotionally, but part of the problem is the result of the clash. She isn't doing what you ask, probably because she's busy playing with a toy or something. Then, when she fails to obey, you take away the toy. It makes sense to an adult, but not to a child. She is trying to be a little more independent, so she is choosing to keep the toy, and the toy gets taken away. That is REALLY FRUSTRATING, hence the tantrums.
So, here's what I recommend. When there is something she needs to do, then she needs to do it. You tell her to do it, and she ignores you because she's busy playing with her toy (or whatever). You tell her you are going to count to 3, and at 3, she must do it. Your count, 1, give the command again, 2, give the command again, and 3. On 3, you simply pick her up, and bring her to the chore, or whatever it is, and then even if you do what you asked her to do, she will have gotten the idea that when you tell her to do something, she puts down her toy and does it. Then you THANK HER, and PRAISE her for doing it, and say, "Now you can go back to your toy !!!"
the idea is to reinforce the behavior you want, not cause behavior you do NOT want to have to deal with. If she is angry, that's fine. Let her take her toy and go to her room. It's okay to be angry, but it's not okay to hurt others with angry behavior. You can even tell her that you understand that she is angry. Tell her it's okay to be angry, but if she can't behave nicely, she needs to go to her room until she can behave nicely. We discipline behavior, not emotions.
By disciplining this way, you are requiring, and forcing actually, the behavior you were trying to get. You will cause some turmoil, and you may get emotionally involved and angry, too, but you are still enforcing and reinforcing the appropriate behavior. She'll get the idea. And by starting at age 6, you will have taught her to obey you before she is old enough that you can't really enforce the behavior.
But, realize that what you are telling her to do, needs to be reasonable. If you are asking her to go to the refrig and get you a soda or something because you are too lazy to stop what you are doing to get it -- then you're the one out of line. (that's just an example) That's a personal request and should be stated as a question, with a please. A behavioral demand may also be stated politely with a please in it, but it is definately NOT a question. Never ask a question, giving your child a choice when you don't intend to give them a choice. Don't say, "Would you please go and do this ?" when you mean to day, "Go do this!" Don't provide a choice of behaviors if you don't intend to.
(since it's a problem right now, I'd probably take the pleases out of commands. You can add them later, when you want to reinforce politeness. What you don't want to do is confuse your daughter. You want her to know when you are offering a choice and when you are requiring a particular response.)
Good luck ! Behaviors like this come in stages -- generally ever other year. We reachout and test our boundaries as we grow up, then we reach a point where we stop pushing, and consolodate our space, to be followed by a year of pushing again. Generally this happens every EVEN year, 2, 4, 6, 8, 10, and lucky 12, when a girls' hormones also begin to kick in. The good news is that the odd numbered years tend to be a whole lot more fun for parents !!!
So hang in, try to be consistent, try to be sure your discipline reinforces the behavior you want to have occur, and don't get too down on yourself. parenting all day long every day is the hardest job in the world. They hear your voice all day long, so it becomes easy to tune out. But we hear their voices all day long, too, and can tune them out. . . . so try to find times when you can really put everything else down and do something fun together, whether it's a walk in the fall to notice which trees are turning first, and which ones are still green, then walk again to see the changes, or it's a game or puzzle you do together.