Anyone else can't face sleep training child number two?

We sleep trained my now-two year old when he was six months (it worked at first for six months or so, then we had to redo, then we sort of lost our nerve and now we're on a sticker chart and big boy bed, so things are OK).

We had said we'd plan to sleep train my little girl at four months. Tomorrow she turns four months and we're both losing our nerve at the idea of letting her cry! I don't know why but I just don't think I can do sleep training again. Am I crazy? Have I become a softie? Is anyone else having this issue with a second (or beyond) child?