Tough decision

Last night we began what has been one of the hardest things I've done so far as a mother. This latest challenge-having Charleigh put herself to sleep. She will be 6 months old this Wed and the "style of parenting" that we found most closely matches our beliefs encourages establishing a base of letting your child know that you will respond to their cries and needs pretty much without hesitation for the first 6 months or so of life. During this time it is believed that you can't "spoil" a child as they are learning about you, their parent and the world around them. The bedtime routine thus far has been quite relaxing and enjoyable. It's been comforting as a mother to have my warm, well fed baby fall asleep in my arms. I'd slowly lower her into her crib and sneak out of the room as she slept. However, as she's gotten a little older she would wake up when we set her down and we'd have to begin the whole little routine over. Once we finally got her to sleep we felt like we'd accomplished a great goal. The last 6 weeks have grown increasingly complicated as after going to bed around 8:30, she'd wake up at midnight, 2am, 4am and 6am. I was convinced she couldn't possibly be hungry each of these times, but she would nurse and fall back asleep so I thought- problem solved. It wasn't easy on my part and I was getting little sleep. We believed she was reverse cycling. So I began feeding her every 1-2 hours during the day and trying to reaffirm the fact that daytime is for eating and nighttime is for sleeping. After about 10 days of doing little other than nursing her there had been no difference in her night time sleeping habits. I've read and and read and read online about how to get your child to sleep for longer stretches through the night. The ONLY thing we were not doing was letting her fall asleep on her own. As a breastfed baby I wasn't sure HOW exactly to do this, as any fellow breastfeeding mother knows, they tend to fall asleep so peacefully while nursing. So for the last two nights as she's slightly awoken while being set into her crib we leave the room and wait. Last night was already worse than tonight so far as I sit her composing this. Last night she cried for about 30-40 mins. Her cry breaks my heart and as any good mother knows...you know you're doing the right thing..but it doesn't make it ANY easier. Tonight there was about 20-30 mins of crying. Of course the dog kinda messed that up with a barking fit because of our crappy neighbors. (Side note- it's 9:40 on a Sunday evening....and 13, yes 13 children are jumping on a trampoline and playing in the backyard next door to us). Last night Charleigh was up from about 1:20-2:30 crying. Dan turned off the monitor, closed the bedroom door and sat up playing video games. Every 10 mins he went in and talked to her, touched her, but did not pick her up. She won't take a pacifier so her cries were only partially muffled by his attempt to spare my motherly heart the pain of my babys cries. Around 2:40 he was able to calm her enough that she stopped crying...once she did that I went in and fed her. She ate and fell back asleep till 7. AMAZING PROGRESS!! I was prepared for much worse. It was hard to keep telling myself that this was going to be better for both of us, even though I know her gaining this ability and reaching this milestone is important.
I know this is only one of many difficult changes/growing pains/milestones that will both hurt my heart as a mother yet excite me when it's become a positive in our relationship as mother and daughter.