Why does some people can sleep instantly as soon as they hit the bed. Like a auto system in their body. I'm wondering why -m always having a hard time sleeping. It is a big frustration each time I face while I need to snooze.

In younger day, when I babysit my cousins, they can doze off within 30 seconds as soon as they close their eyes. For me, it might take more than 1 hour. So so unfair!!!