Don't try to stop it, have you ever heard someone tell you not to think about something, just let yourself unwind and allow the chatter to fade out naturally, it will go faster the more you don't try to stop it. It's probably tough at first but there are other ways around it if you are struggling to relax. Give yourself 30 minutes before bed to relax, have a bath or something relaxing, try not to have many bright lights near you. Then focus on one thing, your breathing or the sensation of your back on your bed. Perhaps count down from 100, getting more relaxed with each number.
Basically allow yourself to chatter of focus/distract yourself.

Good luck and keep it up!