"Each one should test his own actions. Then he can take pride in himself, without comparing himself to somebody else, for each one should carry his own load." NIV translation
There are some burdens that we cannot help with as people have to deal with their own actions on the final day. On that day, we will all give an accounting of our actions in advancing the gospel of Jesus Christ.
"Anyone who receives instruction in the word must share all good things with his instructor." NIV translation
Those who teach the Word of God should be supported by those that he teaches. We have heard the quote that the worker deserves his wages and the same principle applies to those that labor in teaching the Word.
Even so, there were many times where Paul had the right to expect wages but instead worked as a tentmaker in order to not be a burden to the believers.
"Do not be deceived: God cannot be mocked. A man reaps what he sows. The one who sows to please his sinful nature, from that nature will reap destruction; the one who sows to please the Spirit, from the Spirit will reap eternal life." NIV translation
When we look with our physical eyes, it may seem that there are some who prosper without Jesus in their lives. They may have fancy homes, fancy cars, or be famous and adored by those around the world while many who wholeheartedly serve the Lord seem to have very little. This is the same thing that the worship leader, Asaph, experienced in Psalm 73. When he took what his physical eyes saw to God, he was shown their fate through his spiritual eyes. That is what Paul is reminding us of in this passage. Though it may seem like many are being blessed and reaping rewards of this world, in fact, they are headed for destruction. While it may seem that many who are walking in the Spirit serving the Lord are poor, they have eternal life and are storing up treasure in heaven.
"Let us not become weary in doing good, for at the proper time we will reap a harvest if we do not give up. Therefore, as we have opportunity, let us do good to all people, especially to those who belong to the family of believers." NIV translation
Sometimes, it can seem like a long season of planting and tending the field but, if the farmer continues to take care of the field, there will be a harvest at the proper time. The same is true for our acts of service to the Lord. Many times we may think that we are not making a difference in the lives of those that we come into contact with but, if we continue, we shall see a harvest for the kingdom. We plant into the field of the unbeliever's heart and we tend to the field of the Christian's heart.