It is a toughie. You obviously want them to sleep but I would be careful to get them too reliant on anything external- rocking, white noise etc obviously gets them to sleep easier but they will eventually get to expect it and wont sleep without it. The reality is that as long as they are fed, watered, dry etc and they are tired they will sleep. If they aren’t any of those things then they won’t. As they get older you can obviously sleep train them but when they are newborns you sort of have to let them decide for the first wee while.