This is such a difficult subject, because it is so hard to get it right.  It never worked for me, and as I result, I felt that 50% of the time I was sleep depraved, and feeling very not with it.  How can you be when you are always tired.  I tried the controlled crying buy my daughter could cry for hours, literally.  It was amazing how much energy she had.  I thought she would get ill if she continued, but she was so head strong, and just did not give up.  After a couple of hours of going back and forth, I gave in to her.  This went on for ages.  I really think it depends on the child.  I suffered so  many years, with it.  And then when she started sleeping through the night, I got pregnant again....and it all started up again. DD no 2 was just the same.  So it was really hard.  Sadly this went on for year,s and then I go insommia.  But the good news is I am better now.