When we were young, my brother and I used to play this game where one of us would crawl head first into a sleeping bag, and then the other guy would wrap up the open end and sit on it.
Whoever stayed trapped the longest was the winner.
Now, you would think that a person could stay inside a sleeping bag for hours. There is no danger of suffocation. Air is easily transmitted through the fabric. In fact, it is not even as dark in there as you may think, because a little bit of light leaks in around the zipper. After a while, you can see quite well.
The problem, however, is that you are trapped. And after a while, that is all you can think about.
Claustrophobia sets in long before the actual "physical dangers" of being trapped in the sleeping bag become serious. When thoughts like, "I can't move," "I can't breathe" or "I have to get out" start to dominate your thinking, then you are done. I think our all-time record was something like 20 minutes. (If you try this at home and break that record, write to me as I would like to hear about it).
Of course, claustrophobia always makes us exaggerate the danger of our circumstance. Have you ever known someone who would not go on a cave tour because they were sure that the cave was going to collapse, and that they would be stuck down there? It is an irrational thought because millions of people go on cave tours ever year without trouble, but when your mind starts thinking fearfully, then the danger is magnified beyond reason.
A similar thing happens when I "over focus" on myself in my life: I become spiritually claustrophobic. I start thinking only about all the perceived dangers and all the negative things in my life, and I start to panic. Dread washes over me and I feel like giving up even when things are not really that bad.
The cure to spiritual claustrophobia is simply to look out. When we focus on someone else, when we try to help others with their problems, it has a way of putting our lives back into perspective. In fact, I think that is one of the reasons that the Bible contains so many "one another" passages. When we love one another (Romans 13:8), serve one another (Galatians 5:13) or encourage one another (1 Thessalonians 5:11), it gets the focus off of me and onto you and that makes all the difference.
When I focus only on me, inevitably, I feel trapped. My problems magnify and my life seems somewhat overwhelming. When I focus on others, it opens my life to new joys, new possibilities, new opportunities and new hope.