“Therefore if there is any encouragement in Christ, if there is any consolation of love, if there is any fellowship of the Spirit, if any affection and compassion, make my joy complete by being of the same mind, maintaining the same love, united in spirit, intent on one purpose.”

‭‭Philippians‬ ‭2:1-2‬ ‭NASB‬‬
In the past I have taken "being of the same mind" to mean, "be like minded with each other," but feel I received fresh light on the deeper meaning of this exhortation recently. In much of Philippians chapter 1, Paul has detailed how his suffering has played out for the furtherance of the gospel, and how it's caused him to rejoice (see verses 12-30 in particular), and he concludes the chapter by exhorting the church to be prepared to suffer for the sake of the gospel, just as he has:
“in no way alarmed by your opponents-which is a sign of destruction for them, but of salvation for you, and that too, from God. For to you it has been granted for Christ's sake, not only to believe in Him, but also to suffer for His sake, experiencing the same conflict which you saw in me, and now hear to be in me.”
‭‭Philippians‬ ‭1:28-30‬ ‭NASB‬‬
So when he says "make my joy complete by being of the same mind," he is not telling them simply to be like minded with each other; he is telling them to be like minded with him, specifically in regards to suffering!
What I take from this is that Paul wants me to be of the same mind as him when it comes to trials and difficulties in my Christian life. Don't be alarmed when I face opposition. It is granted not only that I believe, but also that I suffer for Him. Paul cites his own experiences as an example and encouragement to the church at Philippi, that they might take heart in the face of their own opponents. 
Our flesh will always tell us to be surprised when opposition comes: "Surely a precious child of God shouldn't have to endure this (fill in the blank, heartache, frustration, embarrassment, etc)." But Paul is telling us as believers to renew our minds, and have a mind which is prepared to suffer rather than be surprised by suffering. Peter says essentially the same thing:
“Beloved, do not be surprised at the fiery ordeal among you, which comes upon you for your testing, as though some strange thing were happening to you; but to the degree that you share the sufferings of Christ, keep on rejoicing, so that also at the revelation of His glory you may rejoice with exultation.”
‭‭1 Peter‬ ‭4:12-13‬ ‭NASB‬‬
Suffering shouldn't be unfamiliar to us as Christians! We have to put to death those feelings of surprise and alarm that well up in our flesh! It's not "some strange thing;" it is part of our calling. Jesus Himself said “... you will be hated by all because of My name," (Luke‬ ‭21:17) and “If the world hates you, you know that it has hated Me before it hated you.” (John‬ ‭15:18‬) And in fact, Peter tells us that we're not only being like minded with Paul, but also with Jesus, when we are prepared to suffer: "...Since Christ has suffered in the flesh, arm yourselves for the same purpose..." (1 Peter 4:1).
Rather than be surprised, I should "keep on rejoicing," as Peter says, believing that my rejoicing in the last day will in some way be in proportion to the degree to which I have shared in Jesus's sufferings. The more I have shared in Christ's sufferings, the more I will rejoice in the last day! I want to believe this with strong faith, and expect that faith to change my attitude towards every unexpected trial that pops up. 
So far from being alarmed, as I grow stronger in faith, I can "consider it all joy when I encounter various trials," rejoicing in the hope of exultation!