We never "trained" her to sleep all night like letting her cry it out. I know some people do that and that works for them and again, do what you gotta do. Alice's little personality just dictated what we did. I know some babies just wanna be held and cry 'til they are but she's been pretty basic needs/independent from the get go. Mostly cries for food, fusses when she needs a nap. When she was up at all hours I'd feed her and hold her, I couldn't let her cry for long. Thankfully she outgrew that and that's what allowed me to try the whole sleeping in her room thing.
I have heard about the 4 month sleep regression thing so we'll see what happens then. I may be singing a whole other tune then.