Puzzled about perseverance?

1 Corinthians 9:24-27

19 Though I am free and belong to no one, I have made myself a slave to everyone, to win as many as possible. 

20 To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. 

21 To those not having the law I became like one not having the law (though I am not free from God’s law but am under Christ’s law), so as to win those not having the law. 

22 To the weak I became weak, to win the weak. I have become all things to all people so that by all possible means I might save some. 

23 I do all this for the sake of the gospel, that I may share in its blessings.