This goes right along with the series that I am preparing for the members of my church. Once God has given us grace, it can never be repealed. Yet because of our failures and testings, we can lose our assurance, peace, comfort and joy. But we will never be "un-born again". True, our sins hide God's face from us, and we feel very alone without the fellowship of God. But those who have received true grace will not allow discouragement to cause them to give up and run away from God, but they will run to Christ and hold on to Him with all their hearts and with a "trusting" faith, even though they might not have faith based on God's fellowship with them. When we are out of fellowship with God, true believers will long for it as in a dry and thirsty land. They will cry out to Him. In the Song of Solomon the woman says, "I looked for my beloved and could not find him."
There are times when clouds obscure the sun and the days are grey and overcast. But this does not mean that the sun has stopped shining. It is just that we can't see it. I went on a plane trip recently. At the airport the sky was overcast, but when we got to 35,000 feet, we had broken through the clouds and flew in brilliant sunshine. This can be our experience in God. His face can be hidden from us, and clouds may obscure our assurance, but our salvation and our standing with God is still there. It is just that we can't see it. Then, as in the day when the clouds roll away and the sun comes out, so the day comes when the clouds of doubt and fear roll away and we see the face of God shining on us once again.
So there is no real reason to be discouraged and cast down if we can't see the face of God or sense His presence with us. We maintain our "trusting" faith in Christ and get on with doing the will of God in our lives until the sense of fellowship returns. So we keep reading the Bible, praying, fellowshiping with other believers, going to church, being involved in worship, doing good for our neighbours - all through trusting faith, because we know that the grace of God is not diminished for us. It is still there.
Some go doubting all their lives, and even at the point of death, but they are in heaven today. Some others have a false confidence and think they have "arrived", even though they don't walk with Christ, or pray, or go to church, or do kind things to their neighbours. They are in hell today. A person can have doubts and fears yet have true grace. Others can be totally confident in their religious yet have no grace at all. This shows that whether we are confident and comforted, or are doubting and fearing, if we are converted to Christ and have grace, our salvation is secure.