Positive thoughts for sleepless nights

Periodically I wake up in the middle of the night and have a hard time getting back to sleep. It’s like I can’t turn off my brain. Usually it happens when I know I need to get a good night sleep for something the next day.
I have been making some big decisions and positive (though scary) changes in my life lately. But it seems like the pattern of over-thinking instead of sleeping is getting worse!
I have tried to come up with positive thoughts to help me feel at peace so I can rest. But inevitably they seem to relate to how I need to sleep in order to function the next day.
This creates a feeling of pressure to fall back asleep, and continuing worry, rather than peace.
Can you give me some suggestions of ways to think about calming my brain without actually ending up in stressing myself out more?