Contentment is always elusive when it’s based upon the pursuit of personal happiness. While the world encourages us to prioritize our own felt needs, realize our dreams, and strive for personal success and satisfaction, there is no lasting contentment in such selfish pursuits.
As John MacArthur explains, that kind of widespread navel-gazing takes a heavy toll on society.
Selfishness is a consuming and destructive sin. The first and inevitable casualty is the person who manifests it, even if no one else is harmed. Because this sin, like every other, begins in a sinful heart, anyone can commit it—regardless of whether there is an opportunity for it to be outwardly expressed. Even when not outwardly manifested, selfishness breeds anger, resentment, and jealousy. . . .
It is an immeasurable tragedy that modern culture (including much of the church) has, largely through the influence of secular psychology, rejected the divinely commanded principles of humility and selflessness. When the supreme virtue is self-love and the supreme purpose in life is self-fulfillment, mutual respect is replaced by disrespect, mutual service by apathy and indifference, and mutual love by enmity and hatred.  John MacArthur, The MacArthur New Testament Commentary: Philippians (Chicago: Moody Press, 2001) 110, 114.
Christians must not succumb to such a selfish lifestyle, and the other sinful attitudes it breeds. That’s why the apostle Paul points our focus away from ourselves.
Do nothing from selfishness or empty conceit, but with humility of mind regard one another as more important than yourselves; do not merely look out for your own personal interests, but also for the interests of others. Have this attitude in yourselves which was also in Christ Jesus, who, although He existed in the form of God, did not regard equality with God a thing to be grasped, but emptied Himself, taking the form of a bond-servant, and being made in the likeness of men. Being found in appearance as a man, He humbled Himself by becoming obedient to the point of death, even death on a cross. (Philippians 2:3–8)
Paul’s life is a testimony to the fact that lasting contentedness is a product of cultivating a selfless concern for others. Later in his epistle to the Philippians, when he told them he had learned the secret of contentment (Philippians 4:10–12), his selflessness was a central component.
In fact, it’s why he commended the Philippians for emulating his outward focus when they emptied their shallow pockets to meet his own pressing physical needs. Paul rejoiced not only in the blessing that their support was to him, but even more so in the knowledge that the Philippian believers were also reaping the rewards of selflessness.
Nevertheless, you have done well to share with me in my affliction. And you yourselves also know, Philippians, that at the first preaching of the gospel, after I departed from Macedonia, no church shared with me in the matter of giving and receiving but you alone; for even in Thessalonica you sent a gift more than once for my needs. Not that I seek the gift itself, but I seek for the profit which increases to your account. But I have received everything in full, and have an abundance; I am amply supplied, having received from Epaphroditus what you have sent, a fragrant aroma, an acceptable sacrifice, well-pleasing to God. And my God shall supply all your needs according to His riches in glory in Christ Jesus. (Philippians 4:14–19)
Pay particular attention to verse seventeen which affirms where Paul’s greatest joy lay: “Not that I seek the gift itself, but I seek for the profit which increases to your account.” John MacArthur says that Paul,
Was more interested in their spiritual benefit than his material gain. Being comfortable, well fed, and satisfied weren’t Paul’s main concerns in life. Rather, he was interested in accruing eternal dividends to the lives of the people he loved. . . .
Paul described the gift he had received as “a fragrant aroma, an acceptable sacrifice, well-pleasing to God” (Philippians 4:18). He was using Old Testament imagery to say, “Not only did you give it to me, but you also gave it to God.” . . . His joy came not because he finally received what he had been wanting . . . but because the Philippians had given him something that honored God and would accrue to their spiritual benefit.  John MacArthur, Anxious for Nothing (Colorado Springs, CO: David C. Cook, 2006) 141–42.
“Spiritual benefit[s]” and “eternal dividends” are the greatest possible rewards we could receive. It’s what Jesus described when He told His disciples to “store up for yourselves treasures in heaven, where neither moth nor rust destroys, and where thieves do not break in or steal” (Matthew 6:20). Those are undiminishing and irremovable benefits that no personal bank account could ever guarantee.
Unfortunately, eternal rewards often don’t excite us like they should when temporal needs seem more pressing. But God isn’t ignorant of our immediate physical needs either. Paul closes his passage by reminding the Philippians that because of their selfless generosity, “My God shall supply all your needs according to His riches in glory in Christ Jesus” (Philippians 4:19). He assured them that God takes an active interest in caring for the physical needs of His people as well. It’s a liberating comfort to know that we can sacrificially care for others, secure in the knowledge that our sovereign God cares so much for us (Matthew 6:26).
Few would argue the value and virtue of selflessness. However, putting it into practice never comes naturally.
Although the meaning is obvious and easy to understand, it is difficult to apply. It is the practical outcome of the exceedingly difficult command to regard others as more important than ourselves.
Among other things, looking out for the interests of others requires believers to “rejoice with those who rejoice, and weep with those who weep” (Romans 12:15), to continually “pursue the things which make for peace and the building up of one another,” to not “eat meat or . . . drink wine, or . . . do anything by which [a] brother stumbles” (Romans 14:19, 21), and to “bear the weaknesses of those without strength and not just please ourselves” (Romans 15:1). It is to “bear one another’s burdens, and thereby fulfill the law of Christ” (Galatians 6:2). The MacArthur New Testament Commentary: Philippians, 114–15.
Paul understood that true contentment only comes through that kind of selflessness. For the sake of our own contentedness, as well as the benefit of the church and its testimony in the world, we need to cultivate that same kind of selfless concern for others.