Sleep Success...and failures!

Calling all parents! Do you ever feel like you finally have the whole sleep thing figured out just to find out that your toddler finds a new way to thwart your effort at a full nights sleep days later? I just finished bragging to all of my "mommy" friends that my 13 month old has (no a better verb is had) been sleeping from 7pm to 6-6:30 am pretty much every night. I guess she must have heard me, because now she is having a hard time going down again and I feel like I am back at the beginning of the "sleep training process" again. Does it ever end? She will at some point develop a routine...right??