The “bridle your tongue” means to control what you say, how you say it, and when.
The words we speak are the indication of the state of our heart. God says that by our word we will be justified, and by our word, we will be condemned. To speak without thinking is as foolish as to drive with eyes closed. God gave our tongue to spread goodness and wisdom to whom we speak to, but sometimes we use it to tear people down, to spread bitterness and to fill them with hopelessness.
We are responsible for how we use our tongue, because it has the power to bring life and death. You cannot claim to be a follower of God when your words highly glorify the evil one. You cannot feast in the table of Satan and kiss Jesus to show others you are one with Him. Our words will show who we really are, for out of the abundance of the heart, the mouth speaks.