Google 'excuse me' sleep method.
It's great for older anxious children who should be sleeping by themselves.
You do your normal bedtime routine and instead of saying goodnight. You say
"Excuse me while I just go to the toilet"
(Or some other excuse to leave the room, make a call, let the dog out, tell daddy something)
You leave for a few minutes then return. You stay for a few minutes and again excuse yourself, repeating the process for longer each time.
For some children the thought of being left for the night is a lot to cope with. If they think it's just short times and know you'll come back soon, they can relax enough to fall asleep. Instead of working themselves up into a state where falling asleep takes forever as they are so frightened.
I found also found a marble jar worked wonders when mine were small. Just an old jar which they decorated and a bag of fancy gems or marbles. Collect a marble for staying in bed all night. Pop it in the jar. When they had 7 marbles they chose a treat. It worked better than a sticker chart. It was the plonk of the marble hitting the jar that gave them such satisfaction.