No matter how strong a man is in the spirit. There is a way to grow more in the things of God. There is a way to strengthen one's self more.
The verse shows us that a man who speaks in an unknown tongue speaks to God. Verse 4 goes on to say that he edifies his spirit. Speaking in tongues was never supposed to be for church meetings but for personal prayer. Therefore, pray more in tongues alone than you do in a fellowship.
The purpose of praying in tongues is to edify yourself.
You are as strong spiritually as the time you spend praying in tongues. Men who are strong in faith have learnt the art of fortifying themselves in prayer.
Prophetic Declarations.
Hallelujah. Amen