@sister & @Sunshine0206, I've had some success with 4-7-8 when trying to get to sleep in the past. In for 4 seconds, hold for 7 seconds, exhale for 8 seconds. You do it five times. Calms the nervous system.
But getting to sleep isn't usually the problem now. Like everyone else it seems, it's repeatedly waking through the night and then the struggle to get back to sleep.
My surgeon says he doesn't normally advocate "sleepers". I don't get why. Good sleep promotes good physical and mental health, not to mention good healing and cell repair. I feel like this aspect of a BC diagnosis is not taken seriously enough.