It took us over a year to figure this out!! Our toddler started sleeping through the night immediately after we did this and hasn't stopped since! If you're stuck in the cycle of sleepless nights like we were, you'll want to check to see if you missed this too.
I was starting to feel like a crazy person spending an hour rocking and nursing my baby to sleep. Then the second I laid her down she would wake back up crying. This method really worked for us! She gets herself to sleep now every night with no crying involved! What to do when your baby has to be held, rocked, bounced or nursed to sleep.