I do concentration meditation. After about 15 minutes most of my mind chatter has dissipated.
Commercial "mindfulness" training is sold as a way of calming the mind. I think it's unwise to approach mindfulness with that expectation. It can have the opposite effect; things can get stirred up, especially if you do longish sessions. Commercial mindfulness is also pitched as being completely safe for everyone. It's not, it can cause trouble, and it's advisable to have a good instructor on hand.