In Phil. 3:8, Paul said” But moreover I also count all things to be loss on account of the excellency of the knowledge of Christ Jesus my Lord,” The things that were gains to him Paul counted loss on account of Christ, because they all issued in one thing, that is, the loss of Christ. Hence, on account of Christ, all the gains were a loss to him.
In Phil. 3:13~14, he even said “but one thing I do: Forgetting the things which are behind and stretching forward to the things which are before, I pursue toward the goal for the prize to which God in Christ Jesus has called me upward.” The Greek word for pursue can also be translated “persecute.” Before Paul was saved, he was persecuting Christ in a negative way. After he was saved, he persecuted Christ in a very positive way. We need to pursue Christ and seek Him even in a persecuting way. Then we will gain Him.