These are instructions from Paul, to Timothy as a front line worker in the ministry: Paul was a good example of "enduring Hardness" as he was beaten, stoned, imprisoned etc. He gave warning to Timothy that similar difficulties would also await him. The second line speaks of not getting involved in worldly pursuits, but rather only those things that pertain to the ministry as a "soldier" of Christ. The next line involves personal spiritual growth, in that disciplines of the body and the spirit if sought after, can be honed to a high degree, or mastered, but only if done lawfully. He goes on to say that God gives the crown for personal victories, but a man who desires such personal growth can only achieve that status if he is striving for it "lawfully" or within the guidelines of Biblical righteousness. The husbandman refers to the worker, (Timothy) in the vineyard of God, and that such workers MUST FIRST be partaker of the fruits, meaning the fruits of the Spirit mentioned in Galatians 5: 22-24.
To sum up, the "credentials" for successful ministry are real and require maturity for any success. All ministries, after conversion, will require self control and humility, with a goodly application of a maturing process.