Hope you are ok Malmaison X
Really great to hear your dd is benefiting from therapy Tinkobell
Machinebee so sorry you went through such an awful time
. Our most often repeated line (usually in relation to tech) is "well once you can regulate it's use yourself, then we won't have to" rinse and repeat X 100
Fudgecakes There are four really bad parenting moments I remember and feel terrible about when I totally lost my temper with dd. Funnily enough, only one of those happened in her teen yrs. The rest was when she was going through a "really challenging" phase at 4 years old when she was"having problems with transitions" (and that's putting it mildly!) I feel quite tense just thinking back to that period tbh because she really pushed the limits.
Having said that though, those moments are not what I feel most guilty about. Overall I feel much worse for being too strict when she was young and for being overall too negative and shouty as a person, which I think came from my own anxiety more than anything else. I've definitely improved as a parent on that score I think but I wish I had known then, what I know now. But hey, hindsight is a wonderful thing! I found Staywithmemyblood's post to be very reassuring. Strict or not, sometimes we can't win!
Fudge it sounds to me like you were pushed to the limit and in those circumstances we do the best we can, we are not superhuman, and as others have said, amd as you have done, we can only apologise, learn, and move on. I'm glad you feel better for venting! 
And yes - agree McMen71 - why do they always just remember the bad bits? Reminds me of taking DD to the zoo one time when she was tiny where she saw lions, elephants, giraffes, chimps etc. Asked about it at school the next day she remembered she had seen "a dead pigeon in a puddle" 
As for Teentimestwo's question about whether I think my relationship with DD will emerge intact after going through teen-hood. I'm fairly confident it will tbh because even in the very very worst of periods now, when she is away, she will still come and sit on the end of my bed and chat late at night, or she will put her head on my shoulder/in my lap while we are watching TV or something (as though the warring bits are happening in a parallel universe
). But whether it will be exactly the same as before, who knows? It has definitely taken some severe knocks recently. I think I need to work on myself a bit more so I get out of this rather grey patch I am going through currently so I can view things more objectively. I feel too tangled up in it to judge properly right now. Teentimestwo is there any outside support available to adopters which enables you to explore this sort of thing? Can you speak to others in the same situation?
Waves to all! Things a bit tense here currently (exams ongoing). And I'm still feeling very flat. It's like I am distancing myself from engaging in anything too fully, post attrition, in case it all kicks off again... .