Don't worry, relax d, my son don't sleep from 21:00 - 07:30 and can keep crying if you don't carry him. I let him cry for two nights then he could sleep from 23:00 - 02:00 then drank milk and then cried again from 04:00 - 06:30. Then drank milk again...
Few days later, he slept better. 8 days later, last night, he slept from 00:30 to 06:30.
Maybe your child need more time to change but i recommend you let he/she cry, otherwise you will be very stressful as me before. Once you have confidence he/she will be changed, your pressure can be released.
I thought if i don't let him cry, he still not sleep at midnight. However, i need to back to work next Monday.