Paul said disqualified for the prize, not disqualified for the gift of eternal life. In context, Paul has been discussing preaching the gospel. In verse 18 he says, "What is my reward, then?" In verses 24-27 he illustrates this thought of his reward by the picture of a race run for the prize. We must pay attention to the context—this passage concerns reward, prize not losing salvation. Salvation is a gift that we receive by grace through faith, not a prize that we race for to win.
Verse 24 settles the matter for me. 24 - Do you not know that in a race all the runners run, but only one gets the prize? Run in such a way as to get the prize. That sounds like running a race in the Olympics. All runners run but only one gets the gold medal. So what happens to the runners that get the silver medal or bronze medal or finish the race with no medal? Are they disqualified from the Olympics or from the prize, receiving the gold medal?
Verse 24 settles the matter for me. 24 - Do you not know that in a race all the runners run, but only one gets the prize? Run in such a way as to get the prize. That sounds like running a race in the Olympics. All runners run but only one gets the gold medal. So what happens to the runners that get the silver medal or bronze medal or finish the race with no medal? Are they disqualified from the Olympics or from the prize, receiving the gold medal?