Don't feel like a failure OP, we all do what we think is best for us and our DC. And children are all different and what works for one, won't work for another.
Mine "slept through" from 12 weeks. For example down at 7, one dream feed before I went to bed and up between 6 and 7. Unless ill or teething etc.
But DC1 would often come into our bed after her dream feed or if she stirred at all. She'd immediately resettle and everyone would go straight back to sleep.
It was not a one off thing, in that I didn't train her and she stayed settling like that forever more, it was a constant readjustment with each developmental leap.
For example, once she could stand (6-7 months), I'd stay by her cot and have to repeatedly lay her back down. When she could talk I'd say quiet time, rest my hand on her and lay her down again if she got up. Then she learnt to climb out of her cot at 13 months (
) so I'd have to stay there until she went to sleep as we took the side off. And that lasted a few months.
I would crawl out of her room on my hands and knees, heavily pregnant, or sit on the landing so she knew I was there.
Once she was older she still chose to come into our bed if she woke up, and occasionally she still does, she's nearly 12 now! 
It won't be for much longer though.
So anyway DC2: slept through from 12 weeks and fell asleep in my or DH's arms in front of the telly until she was 3! We'd then put her into her bed when we went up and there she'd stay, fast asleep, until morning. Once she was three I put her to bed properly at the same time as her sister, no problems at all. She still sleeps like a log at 10 and has never slept in our bed at all.
Both mine were absolute buggers if they had a nap after around 20 months, then bedtime was more like 9,10 or 11pm.
Good luck, it does eventually happen.