If it helps any, even those of us who didn't adopt our kids sometimes feel like we're the worst parents in the world.
My three are teenagers now but there are days I look back on their younger years and marvel that they survived to reach adolescence. I'll probably look back at their teen years with the same surprise and awe!
Maybe no one else wants to admit it, but I will:
Kids stink sometimes.
There, I said it. They push our buttons, they challenge our patience and self-control, and they seem to know instinctively how to deliver a heart breaking knife wound with their words.
They depend on us to recover from wounds which, if our psyches were a bit less secure, would be terminal to our hearts. And somehow, we do. Venting to friends (and people on forums!) is a good start.
You already know you are going to survive this. I just want you to know that you can also survive this with your smile intact. There is light at the end of the tunnel. You might lose sight of it as you follow the twists and turns, but I promise, it is there.