How am I supposed to be able to tell myself that I'm dreaming even though I can't even control what I think in a dream in the first place.

I just don't understand how looking for dream signs will cause me to do this.

For Example, one thing that I notice alot In my dreams is the inability to run.
It happens quite a bit but I can never force myself to realize it's a dream.


I've only been doing this Dream Journal thing since last night so obviously I'm no where near to having a good dream recall but I'm still confused about how I'm supposed to tell myself I'm dreaming.

Can someone explain?