"I have labored to no purpose; I have spent my strength in vain and for nothing," (cf. Isaiah 49:14).
"Everything got its start in Him and everything finds its purpose in Him," (cf. Col. 1:16).
Too many Christians are doing the busy work of God's kingdom as it were and missing out on the spiritual aspect. Now, whatever we do, can be to the glory of God when it's done in His name (cf. Col. 3:17, 23; 1 Cor.. 10:31). Martin Luther said that dairymaids can milk cows to the glory of God. Work had been considered a curse till the Reformation. We must be convinced that we are engaged in doing God's will and fulfilling the ministry He has given us and the mission that we are called to do: Paul said that he desired to complete his mission with joy (cf. Acts. 20:24).
I like particularly what he said in Romans 15:18, "I venture not to speak of but what Christ has accomplished through me." We must realize that human do-goodery or do-goodism doesn't avail much in God's economy and will be counted as wood, hay, and stubble (cf. 1 Cor. 3:15). We must work as the LORD works through us as His vessels of honor, being inhabited and controlled by His Spirit. All our fruits are from Him (cf. Hosea 14:8). All we have accomplished is from Him (cf. Isaiah 26:12). We must not boast of our achievements but trust in God's accomplishment on our behalf. As Martin Luther's hymn, Mighty Fortress, goes, "Did we in our strength confide, our striving would be losing."
We ought to boast in our infirmities (cf. 1 Cor. 12:19). Micah condemned Israel for accomplishing what amounted to nothing and then taking all the credit for it (cf. Amos 6:13): "You who rejoice in Lo-debar, who say, 'Have we not taken by our strength captured Karmaim for ourselves?'" Zechariah warned us not to trust in the flesh in Zechariah 4:6, "Not by might, nor by power, but by My Spirit...." David wrote: "My soul makes its boast is in the LORD," (cf. Psalm 34:2).
Faith is dead without works and they authenticate and validate it but we are saved by faith alone, but only by the kind of faith that isn't alone. True faith produces fruit, not the foliage. And we will be known by our fruits in the eyes of men. We are not saved by works, but not without them either! God has ordained certain works for us to perform in His Spirit and time and we are called to be faithful in doing them. (cf. Eph. 2:10).
A Christian is to be engaged in being "zealous of good works," as Titus 2:14 says, but not in the flesh. That only encourages self-righteousness and self-esteem, not true righteousness and God-esteem. This means ultimately that God uses weak instruments to accomplish His will and to His glory and we should be like Paul who said he'd rather boast in his weakness that Christ may be glorified, for not many powerful, mighty, wise, nor famous are called, but God uses ordinary vessels. When our work is done if we aren't taken before our time, God will call us home to be with Him in glory, as David was after he had completed all God's will (cf. Acts 13:36). May we all check out after proclaiming, "Mission accomplished!"
In the final analysis, God bestows blessings as a gift to us; what we do with them is our gif to God; we must come to the awakening that our righteousness isn't our gift to God, but His gift to us (cf. Isaiah 45:24); no man will be able to boast in God's presence (cf. Eph. 2:9). Soli Deo Gloria!