For some, it's a very real thing.
Joe Heschmeyer over at Shameless Popery has much needed advice for the fearful:
It seems to me that all of us have these sort of fears: we know that we're supposed to do something, but we're dreading it for some reason. If we're not careful, this obstacle gets bigger and bigger in our minds until it seems like an unbeatable giant. The voice inside, telling us to trust God, and that we will be able to overcome these obstacles risks getting drowned out by the voice telling us that we can't,
that our problems are stronger than we are. That's the voice of discouragement and despair, and it never comes from God. We worship “the God of hope” (Romans 15:13), and the devil seeks to undermine this hope by preying upon our fears.
There's one land in particular in which these giants run amok: sin. Before we sin, the devil tries to convince us that it's not a big deal. Afterwards, he tries to convince us that the sin is so big that God could never forgive us, so we might as well give up. He'll then use this as an excuse to get you to sin more: since you're already a lost cause, you might as well have some fun, right? Since we can't beat our giants, why not resign ourselves to Egypt, the place of slavery, where we can at least have some pleasure?
All of these are demonic distortions: we need to be careful to avoid sin, and not to rationalize it; but we also need to be careful to remember that the God of Mercy is infinitely bigger than our sin. It's an insult to God's majesty to suggest that we have a debt so large He can't pay it, just as it was an insult to God for the Israelites to suggest that the Promised Land might be occupied by soldiers too big and strong for God to defeat.
If you find yourself battling these giants, run, don't walk, to the nearest confessional. If your embarrassment or shame at your sin is keeping you from going to confession, don't let it. That's like avoiding going to the doctor because you're embarrassed at how sick you are. Here are four things that you should know...
Go... and know those four things. It's good stuff.