We all want to be remembered for some kind of legacy: The issues are preferably to be a good influence and force in this life. We are worth more than our bottom line or portfolio! We all have a purpose in life that God has called us to and like Paul, we must not be disobedient to the heavenly vision,. Actually, we all make investments in life, hopefully, more in people than in things. That entails being an exemplar or even a father-figure or mentor to someone who looks up to us for leadership: a chance for one-on-one discipleship and investment where it counts for all eternity, not just in a temporal sense; we may find that the best methodology is one person at a time and realizing that the numbers game doesn't all that matter to God but He judges our motives and faithfulness and then He blesses us!
Paul would venture not to speak of but what Christ had accomplished through him! (cf. Romans 15:18). He realizes that he didn't preach or even plant churches without God's blessing and direction: God gave the increase though he planted or watered the seeds. All our fruit must come from Him and all we accomplish through the power of the Spirit; He gets all the glory as Mother Teresa would say, "God hasn't called us to success but to faithfulness!" We all are given certain opportunities in life and must seize the day and make the most of them as we are only stewards of God's blessings, gifts, and provisions.
David was known as a man after God's own heart and proved this by doing and fulfilling all God's will and he did it for the right reasons, not just to gain the approbation of God or favor of men, for He was interested in God's praise, not man's. God has a plan for each of us and we must complete it but it's up to God to fulfill His purpose for us; our job is to be obedient to the heavenly calling. We are to be obedient to the faith and to willingly do God's will, not by compulsion. We must realize that the Christian testimony is one of relinquishment and being subordinate to God's will as the motto of Jesus' life doubtless was: "Thy will be done!"
There is no such thing as a disobedient Christian because we receive Him as Lord and it's contradictory to say, "No, Lord!" He gives His Spirit to those who obey Him (cf. Acts 2:39). Our response must be the continuous "Yes!" and "Amen!" But we cannot say "Yes" to Jesus before we say "No" to ourselves! Note that part of the Great Commission is to teach disciples to obey all Jesus taught. As disciples then we enroll in the school of Christ because a disciple is a learner.
Now being called by God is not for some elite Christians but for them all. God will fulfill His purpose for you! But we must be open to God when He opens or closes doors. We don't aim toward knowledge but changed lives, the whole point of conversion, knowing that availability is the key, not just ability. It's up to God to bless and the results are in His hands, not ours! Remember: Our life is but a staging area or tryout and audition for eternity and the chords we strike may vibrate for all time; we will be remembered in some sense but hopefully for goodwill toward our fellow man and faithfulness toward God.
We must bear in mind that we will be judged for our works (cf. Romans 2:6) whether they are worthy of reward and not wood, hay, and stubble to be burned in the fire (cf 1 Cor. 3:15). Our faith is not judged, for that is the gift of God, but what we do with it as our gift to God; in essence, God rewards us for what He accomplishes through us. It's not about human achievement but a divine accomplishment that matters for eternity. The point in life is not to leave a material legacy or even to be remembered, but to make a difference as far as Gods' will goes--to fulfill all His purpose for you and bring glory to His name.
In sum, we must acknowledge that we are being used by God for His purposes as either a vessel of honor or dishonor, which shall not fail; we must not boast as if we have done it of our own accord and independent of God's blessing on our task. Soli Deo Gloria!