Paul is not ashamed of his personal struggling as a servant of the gospel. Everything which is worthwhile will involve some kind of suffering (the word used here is 'agona'). Examinations, athletics, construction and school teaching - they all have rewards when done excellently, but they will all involve struggle and suffering. Much time is sacrificed, skills are painfully refined, outcomes are clarified, strategies are devised, problems are anticipated; and everything is committed to the task irrespective of the cost - because the outcome is important.