Hindsight, while necessary to avoid disaster, I suppose, can be an evil, evil ability. Looking back and wishing for otherwise is as useless as trying to teach a toddler to walk by yelling, "It's easy! Just put one foot in front of the other!"
Everything seems obvious from a distance. But, you know, some things just have to be lived through. Some falls have to be taken, and though we may repeat our habits, our destructive patterns, over and over and over again, eventually we find a moment between them, and eventually that moment will be long enough for us to gain some perspective. The danger, though, is not forgiving ourselves in that moment.
Forgiveness is the antidote to destruction. Forgive yourself as often as you can and then move forward--no looking back.