Jesus said in John 14:27, that he leaves his peace with us. But he also said, that we should not let our heart be troubled.
What happens, if we let our heart be anxious or troubled in the storms of life? Well, even if Jesus gives us his peace, we can not fully experience it, if we let our heart be troubled and influenced by the storms and difficulties of our life.
If we look at Philippians 4:6, 7 we can see that Apostle Paul was saying the same thing.
First he said that we should not be anxious about anything. Then, after that the peace of Christ will guard our minds and hearts in Christ Jesus.
We see the same principle. First, we have to decide, to believe the Word of God, for any situation or difficult circumstance in our life. If we decide to do that, and if we are willing to do that, then we will experience the peace of God, in all its fullness.
We can not allow the troubles of our life, to make us anxious, by us not believing the Word of God and his promises, and to expect to experience the peace of Christ.
His peace is always there for us, but we decide if we allow the troubles around us, to take control of our thinking and believing, or we decide to believe the Word of God and his promises.