A person who speaks in tongues is strengthened personally,……..
1 Corinthians 14:4 NLT

In other words, speaking in tongues empowers your Spirit, energizes your innermost being and increases your fire.
You have to get filled with Spirit all the time. You can do it on your own through fellowship with the Holy Spirit.

And be not drunk with wine, wherein is excess; but be filled with the Spirit; Speaking to yourselves in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord;
Ephesians 5:18-19 KJV

Many Christians are light already but not the burning type of light, therefore flies can still perch on them. In other words, sickness can still have access into their lives. You become dangerous to the devil and his demons the moment you become a burning and a shinning light because the intensity of the heat radiating from your Spirit will be too much for them to handle.

It’s not enough to shine but we need to also burn. This is the reason why many people experience satanic oppression in their lives all the time, yet they are Christians. Understand the light of the gospel may reveal the truth to you but the enemies will not just fold their hands watching you enjoy them. But with the fire of the Holy Ghost, they have no choice but to flee.
Become a burning and shinning light always, Satan will see you and hind himself. You are more powerful than you can ever imagine. The world is waiting for us to display the power of our heavenly Kingdom.