Every time evil doesn't get a foothold in our lives, we win.
Sometimes bad things happen to us, and we are hurt or betrayed or savaged by life. But there is a difference between being harmed and being ruined. Harm comes to everyone, but Christian people find victory in Christ to avoid utter ruin. It is Christ who sustains us, delivers us, buoys us, and restores us to our full humanity such that we can say, “I'm devastated, but not bitter (even though I should be) because of what Christ has done for me.”
This is what I mean by keeping Satan from getting a foothold. Bitterness is a foothold. It is a cancer that eats your soul from the inside out. You will certainly be harmed in this life. That's the bad news. But the good news is that harm doesn't have to ruin you. If you welcome the Spirit and invite him to heal you from the inside out, you can gain wisdom and understanding and even some spiritual health. But if you refuse, and allow that harm to rot and fester in your spirit, then you will turn bitter. That bitterness—far more than the original harm itself—will ruin you.
You achieve victory when you refuse to be bitter.
Here's a three-part reminder I use to remember how this works and identify the ways Christ is winning in me:
I'm a _________, even though I should be ________ because I can see ________.
I'm a (forgiver, peacemaker, friend), even though I should be (resentful, vengeful, hostile) because I can see (Christ's healing power, Christ's eternal joy, Christ's peace that passes all understanding).
Rachel was a little girl in our church who died of cancer before her tenth birthday. Her father, Frank, had every right to be angry and bitter. He had prayed and begged God to heal his daughter and God had not. None of us understood why not, least of all Frank, but Frank understood that Rachel's suffering was over, and she was now in the presence of Jesus. Frank understood that Rachel had already received her (final) victory. Understanding that was Frank's victory. Refusing to be angry with God, question God, or distance himself from God was further victory in Frank's life. As a result, nearly two decades later, I can testify to the fact that Frank is one of the most profoundly happy and generous people I've ever met. But he had every right to be reclusive and miserable. The difference was that Frank chose not to exercise his right to unhappiness, but to claim victory in and with and through Christ.
He refused to let the devil get a foothold, and as a result he has a life most everyone would envy. That life didn't come easily, but Frank was faithful and disciplined, mindful of who God is and what he's done and—focused on that—it was more than enough for everyone to win in the end.