This is where our "2 minute check" was born, and it continues to this day....and my dd is 10!
Go into bed, say goodnights, etc....and say "I'm going to brush my teeth and come back in 2 minutes". Always return. In the beginning, return in just 60 seconds....as long as it's BEFORE the child gets upset and calls out. In time, the child starts to know fully well that you WILL return, and they allow themselves to relax. In about 2 weeks time, my dd would roll over and say "see you in 2"....totally relaxed and ok. We'd put on our pjs and return to her. Or switch over laundry and return. Always leaving with "see you in 2". In time, she was asleep by the 3rd check, feeling totally safe.
These days, our "2" is more like 8 or 10....but she is able to just roll over and chill. 50% of the time, she is alseep at the check, and always at the second check.
HTH