Is there a logical flow in 2 Timothy 2:4-7? No man that warreth entangleth himself with the affairs of this life; that he may please him who hath chosen him to be a soldier. And if a man also strive for masteries, yet is he not crowned, except he strive lawfully. The husbandman that laboureth must be first partaker of the fruits. Consider what I say; and the Lord give thee understanding in all things. (2 Timothy 2:4-7, KJV)


These statements seem disconnected to me. Considering that Paul is asking Timothy to consider these things, I would think there is some connection between these counsels.
Just like teachers today, Paul is using an illustration. The form his illustration takes is three examples of people who work hard, to show what working for God in Christian ministry is like. There are slight differences in what each example tells us about ministry. To understand it you need to read it in context:


  2:1 You then, my son, be strong in the grace that is in Christ Jesus. 2 And the things you have heard me say in the presence of many witnesses entrust to reliable people who will also be qualified to teach others. 3 Join with me in suffering, like a good soldier of Christ Jesus.  
  
  4 No one serving as a soldier gets entangled in civilian affairs, but rather tries to please his commanding officer.
  5 Similarly, anyone who competes as an athlete does not receive the victor’s crown except by competing according to the rules.
  6 The hardworking farmer should be the first to receive a share of the crops.
  7 Reflect on what I am saying, for the Lord will give you insight into all this.
  
  8 Remember Jesus Christ, raised from the dead, descended from David. This is my gospel, 9 for which I am suffering even to the point of being chained like a criminal. But God’s word is not chained. 10 Therefore I endure everything for the sake of the elect, that they too may obtain the salvation that is in Christ Jesus, with eternal glory. (2 Timothy 2:1-10, NIV)


In verses 1-3 Paul exhorts Timothy to continue in his ministry through the strength of God's grace. That work is primarily about teaching and passing on the message, but as verse 3 says, the work will involve suffering, like a good soldier of Christ Jesus.

So he then gives his three examples. Here's what I think they communicate:


Christian ministry is like serving as a soldier because it requires a distinct lifestyle. Timothy has to avoid being distracted away from his work by 'civilian affairs', because he isn't working for himself, he's working for God. The Bible talks about this in many other places, such as in Matthew 6:24: you can't serve money and God.
Ministry is like athletic competitions, because you can't cheat. You can't take short cuts, you can't abuse your co-athletes. And like a race, ministry has a reward at the end.
Ministry is like a farmer. When the work is done we will see the results. But farmers do have to work hard, just like we do.


A common theme through these three examples is delayed reward, which is where Paul goes in verses 8-10. Paul is suffering for his ministry, but he knows it is worth it. He endures it because through it he is helping other people obtain salvation and eternal glory. His reward is to share God's glory with his new Christian brothers and sisters.