Me too, 由day one 開始佢就自己一個人瞓自己間房, 當熄燈閂門會自己瞓, 但 到7 ...
1st theory: 狠心 + 忍心
I wont open the door no matter how hard they cry, until I hear they turn and face down ( the sound of crying is difference). After 3-5 times, they would know it is not workable to draw our attention and stopped. And you must trust the bio-clock of the baby,actually they would know when to do what and when shld go to bed, try to put them to bed at the same time everyday and set is as routine.
2nd theory: do sth before bed and make as routine
Jux like wht I said, set routine and training is something that should follow strictly. I would let my kids have milk, after that will take them to toilet then change clothes and next clean face and teeth, finally put in sleeping bag==> After you have done all these steps, they would know it is time to go bed, they would play less and prepare to sleep by themesleve.
I have used the above methods to train my 2 kids and so far is successful (4 yrs and 9.5mths),hope it is useful to you too