The next night was 2 hours, then 1 hour, then 30 minutes, and then she figured it out. The first night we tried it she cried for 4 hours before sleeping and we felt like absolute monsters for leaving her alone. We tried the Ferber method at first, but us going into the room seemed to agitate her more, so we eventually went with extinction. Sleep training was pretty rough, my girl is stubborn like her mother. We coslept for a long time and it worked well for us.