Well, maybe the better way to look at it, if I may, is if we are "sinning"(besetting sins) we are not "walking in the Spirit".
When we are walkng in the Spirit, we are in communion with the Lord at the level that He requires of us.
Anything less than that is sin. And you and I know what the end result of sin is.
I dont think the Holy Spirit within us just jumps out of us when we sin, unless we become completely bound by sin.
Jesus(having the Holy Ghost himself...
Luke 4:1) BECAME sin for us on the cross and was conseqentially forsaken by God before he died. Thats what sin will do if we let it "dominate" us.
The Holy Ghost may leave a backslider or it may lay dormant in a brother or sister that loves God and are miserably bound by a certain sin. The Holy Ghost within them is trying to empower them to repent and walk in the Spirit as the very reason we have it is in the first place.
That is where those good ol wonderful trials come in.
After we get the Spirit, we immediately are put into the PROCESS.
God puts us through trials, to root out the hinderances(sins) that keep us from walking in the Spirit. AND THIS PROCESS OF GOD IS RELENTLESS.
The Spirit of God will leave no stone unturned in our lives to get us exactly where He wants us to be in Him.(only if we allow Him to)
BUT can you even imagine how GLORIOUS it would be to KNOW we are in perfect communion with The Lord. If we allow the Lord to COMPLETELY take over our lives as He desires...
We will personally know what JOY UNSPEAKABLE AND FULL OF GLORY is for ourselves. ALL THE TIME.