I can do everything through him who gives me strength.
Paul writes to the Philippians from prison to thank them for the gift they had sent him upon learning of his detention at Rome. Paul has gone through a lot by this point or had more than he needed. He has learned to be content with whatever the circumstances he is given. Whether he is locked in a house or chained to a roman guard, he finds the optimism and a special strength in a situation.
This verse is not about us or what our strengths should be. Beginning in Philippians 4:4-7 Paul says to rejoice! Let your gentleness be evident to all. The Lord is near. Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God. And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus.
This ties in to the full Armor of God that Paul mentions to the Ephesians. With the breastplate of righteousness to guard my heart and helmet of salvation to protect my mind, I can rise up against evil, with him who gives me strength. Paul mentions our minds repeatedly throughout his letters because he knows how powerful our minds are and he wants us to protect the most powerful organ. 2 Corinthians 10:5 tells us we demolish arguments and every pretension that sets itself up against the knowledge of God, and we take captive every thought to make it obedient to Christ. If we expose ourselves to the elements that are against Christ and our faith then we are exposing our hearts and our minds to absorbing those evil ways. Our children are a prime example of this lesson. They watch television where they see attitude, drama, and violence and they think because they see it on TV that it is alright to behave that way. If we expose ourselves and our families to certain behavior, don’t be surprised when that behavior is repeated. Make a difference and remove yourselves and your children from these elements. Turn off the television, refrain from gossip, and protect your minds and your hearts.
Finally brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable – if anything is excellent or praiseworthy – think about such things. Whatever you have learned or received or heard from me, or seen in me – put it into practice. And the God of peace will be with you. Philippians 4:8-9