Imagine Paul taking a saw and cutting through your chest, and then taking a scalpel and piercing your heart. Imagine that he is checking there for both life and cancer. He wants to remove the cancer and preserve the life, make it grow even. That is what Paul is doing as he does a "Kingdom checkup" on any Christian willing to submit to it in Philippians chapter 2. But beware! This is no minor surgery.
Vs. 3 - "Do nothing out of selfish ambition or vain conceit, but in humility consider others better than yourselves." - Do nothing selfish. That is our aim. It is not impossible, but it is so counter-cultural that even Christ-believers tell each other that it is. We are the ones that should look at others and love so much that we see ourselves as less.
Vs. 4 - "Each of you should look not only to your own interests, but also to the interests of others." - You can have interests. You can even look to them, but never at the expense of other's interests. Some Christians go days without sincerely looking at another person's welfare.
Vs. 5 - "Your attitude should be the same as that of Christ Jesus." Imagine for a minute if Jesus decided to live his life out of selfish ambition, made decisions from a place of conceit, and decided to forget other's welfare and just take care of himself. There would have been no cross, no grace, no love for the world.
Jesus' attitude would have tragically been the same as that of humanity. But Paul is calling humanity to have the attitude of Christ. May we set our hearts on others.