Serve with the spirit

Romans 1:9 KJVS

[9] For God is my witness, whom I serve with my spirit in the gospel of his Son, that without ceasing I make mention of you always in my prayers;

What does this mean?

I serve God with my spirit according to the good news of His son Jess s Christ. Not according to how I feel, what I think, but according to the good news of His son.