When twin 2 was 10 months old he had tonsillitis. It was horrible. A couple of nights into antibiotics he wouldn’t stop crying when we put him down for the night. We waited 10 mins, we went in and held him, put him down , and the crying continued. We brought him downstairs for 20 mins and tried again. Crying. Not being able to bear it, still crying at bedtime, I brought him into bed with me. He carried on crying. He just wasn’t happy! So we took the difficult decision to put him back in his own bed and let him cry himself to sleep. Not fun! The only thing that stopped him crying was rocking but there’s only so long I can rock a 22lb baby. And if it’s a choice between crying in my bed or crying in his bed then I’d rather give him a decent chance of longer sleep once he’s asleep and not have to share my bed with a baby.
Sleep training is similar. They cry anyway, so they might as well be crying in pursuit of a healthy nap routine.