My first answer to that question, when I read the thread title was, 'love makes a good parent'.
I truly believe that. If you love a child unconditionally, you can get past all the hard times.
We all go through stages in our life where we question if we're a good person. Am I a good mother? Am I a good wife? Am I a good friend? It's natural to ask yourself these.
It's what we do in life, and how we love that's the main point.

I'm sorry you're going through a rough patch with your dd ATM, but it will get better. And you'll think why you even thought you weren't a good parent to begin with