Why does my brain get more active when I try to sleep even though I’m exhausted?

Last night I was completely exhausted. My body wanted to sleep, but my brain just wouldn’t stop thinking.

It kept replaying old conversations, imagining future scenarios, and creating problems that didn’t even exist.

Why does this happen?

Is it just stress, or is there an actual scientific reason our brains become so active the moment we try to sleep?

I’d love to hear your experiences and whether you’ve found anything that actually helps.