Sometimes life gets comfortable. Even when you have a child with special needs or you have a medical condition, there are times of reprieve.
We wish for them, pray for them, and hope for them. These times are the days when life seems normal. In those times, we might not be thinking about it, but the reality is that God's mercy is flowing over us. We don't see him, and we don't see what He is doing, because things are good, but the reality is that His presence is what is keeping us together. He is mercifully making things go well.
Then you might have a hiccup. Maybe you have a relapse or your child gets sick. Maybe life becomes more difficult, and what happens? As a Christian, our first response should be to go to God. Most likely, that is not our first response. We will probably feel anxious at first, and that is not necessarily a sin, but if we take that feeling and start thinking, worrying, and fearing, then we are probably sinning.
It's not hard to go to God. His presence is as real as we are. We can't see Him, so we might forget Him to some degree when the going is good. If only his presence were so obvious to us during the good times as they are when frustration hits. His grace is the reality of His presence during the hard times just as much as His mercy is the reality of His presence in the good times.