Proverbs 27:17 Iron sharpens iron so one man sharpens another

God wants to sharpen us so He allows things to happen in our lives, particularly through other people, especially those closest to us to sharpen us. So those things (ie circumstances, words spoken, deeds done) that our enemy would intend to harm us with God allows for this reason....

Romans 8:28 God works all things together for the good of those who love God and are called according to His purpose for them.

God wants those things to happen not to harm us but to work in us for us to be all He has called us to be.

So when what seem like unfavorable encounters occur we need to be quick to realize that God is at work in our lives. It's not so much about the circumstances as much as what God is trying to accomplish in us so He can work through us.