Here’s what he means. There are always going to be seasons in the Christian’s life where it seems you are not producing spiritual fruit. That’s OK.
Before you become a Christian, you are wrestling with God on the outside, where the fight is obvious. When you become a Christian the fight goes on in the inside. Either way it’s still a fight. We Christians may have the outward appearance that all is calm and collected at times but that’s because the deep wrestle is happening internally.
If you are “wrestling” with things this week… good! That’s the sign of spiritual life!