Holding fast the word of life, so that I may rejoice in the day of Christ that I have not run in vain or labored in vain.
Philippians 2:16 (NKJV)
For some, the responsibility of an evangelist is to proclaim the good news and count how many people are coming to Christ. For the most part, once this task is accomplished, they free themselves from the burden of spiritual accompaniment of believers. They do not contribute to their spiritual progress. For them, this part is the responsibility of the pastor of the church where these believers will join.
When we consider this verse, we clearly understand that Paul does not see it that way. For him, the spiritual progress of believers is as important as their salvation. He knows that after accepting Jesus Christ, every believer must know God through His word in order to develop a personal relationship with Him. This is why he encourages the Philippians to stay in the word. He knows that this is the only way that his work will not be in vain.
Even if this passage was addressed to a specific people, at a specific time, it is still relevant today. Now ask yourself, can Paul boast about you? Can he be assured that his work has not been in vain in you? If so, then you have every reason to be proud of your efforts. If not, then you should try harder, because all these epistles were written for your spiritual maturity.
May the grace and peace of God be with you all.