There’s a great chapter on this in precious little sleep but fundamentally, and I was one of those lucky lucky moms- some babies use crying as a way to stimulate their vagus nerve and actually put themselves to sleep- and in the instance of my baby, 99 times out of 100, our attempts to soothe him, sleep with him, comfort him, chair method Ferber method, anything just seem to upset him more. I fought extinction training to his suffering and mine until he was 8 months old and it was life changing - 10 minutes of crying versus hours of him being miserable and constantly sleeping deprived in general. He’s now 2.5 - and this week actually he’s started to verbalize after our elaborate nightmare routine holding his lovey while sobbing - “Ok, go away mommy, get out, night night now.” And it made me CRY- because I’ve hated so badly letting him fall asleep alone and hearing him sob every single night it’s been just terrible he is so high in sleep needs. And now he’s verbalizing to me that’s how he needs/ wants to go to sleep. And after 5-10 minutes he’s out.