"Make every effort!" That's quite a challenge. But notice where that exertion is to be focused: peace and mutual edification. Both sides of this exhortation are two way responsibilities. I must pursue and share peace if I am going to have it myself. I must edify, and be open to being edified, if mutual edification is going to happen. In other words, we live with other people in God's family. He wants us to be responsible for making relationships work in our spiritual family. He reminds us it will require strenuous effort. But, isn't that true in every family relationship? Love means sacrifice, effort, and concern for others. When we share our love willingly, however, we're much more likely to see it coming back to us!