Update to my original post...
Unfortunately, W2S has not worked on every nap for me. I was so thrilled that it worked on the very first try though all remaining naps on that first day, Mia woke right on the 40-45min mark. I'm continuing to W2S, though it appears it only works for one nap for the day, and it's never the same nap. I try not to get discouraged, but I just wish Mia can get more sleep. And there are days when W2S doesn't work at all.
Is that common? Sometimes W2S works and doesn't?
To YXCHAN - My husband and I used to AP before I read BW. Then we implemented the Four S and after a week or so, Mia can fall asleep on her own. It was a very long week, lots of crying (from both Mia and me), and frustration, but it worked for us, so maybe give that a try. The key is to be consistent. Also, I think we were keeping Mia up way too long, OT, so putting her to bed was really stressful. Now, instead of looking at the clock, I really try to pay attention to her cues. 90% of the time, she goes down without a fuss.
Still today, our biggest problem are short naps. Before reading BW, I was not aware of baby's sleep cycles and that it's very common that babies wake up 45-45 mins. Since I didn't know that, I just thought Mia's naps were over, so I'd pick her up and went about our day. After 15-20 mins, I could tell she would get tired and fussy, and didn't understand why since she just got done with a nap. After all those weeks of me getting her out of her crib after short naps, I think it really hindered her ability to self-soothe and continue napping. Now, I'm battling to get her to nap longer.
In addition to W2S, what other methods can I try to help Mia self-soothe? She is a preemie - 20 wks actual, 16 wks adjusted. Too young for PU/PD?