Writing in Reverse, and How On Earth Does One Self-Edit, Or Self-Evaluate?

I'm quite enjoying writing backwards. I ask myself, where do I want this character to be at the end of the story, and then I write. I refer to things that will need to be added or explained earlier in the story.

Then I ask, how did they get from the beginning to where they are now? What had to happen for the ending to happen as written? Add in the points I mentioned above, and a scene in front of the one I just wrote takes shape. Step by reverse step, I'm finding out where the story is coming from, rather than where it's going.

I may not get anything written tonight. Busy, busy, unfortunately. But I did jot down some ideas, and I got a section of the story worked up for my critique group.

I had another melt down last evening. I looked at my writing and thought, "This is crap. Total, incontrovertible crap."

Then I started writing, forgot about crappiness, and just enjoyed the story.

I keep wondering about my desire for external validation. There is a notable agent that is accepting the first 20 pages from ten local authors for her critique. Even if it weren't out of my budget, I wonder if I would do that. If she said it was no good, I wouldn't stop writing. If she said it was good, I still wouldn't stop. So, why seek opinions?

Obviously because I have no confidence in my own abilities. How does one acquire that objectiveness? All I read (and I read so very much) about self-editing seems inevitably to rely upon one's own discernment of what 'feels' right.

All I know is that when my editor has returned pages to me with lots of green crossings-out, I cannot understand why this was cut and not that, or why this emotional depiction was deemed unacceptable but this other was okay. I remain perplexed.

He tells me I should write more, and thus learn. Well, huh. I wonder how much writing it will take for me to feel confident in what I create?

Do all you other writers get hung up on this? Do you feel you know when you've gotten it right? Do you angst over understanding, or just enjoy the writing and accept the editing?