This is your room. It's a comfortable room. It's the room where you spend most of your life, and it is filled with all that is you.
Some days the light dims a little. Your room feels a little dark. But you don't worry about it because you know that some days are just darker than others. Tomorrow there will be more light again.
Sometimes the light continues to dim by just a little tiny bit every day. Sometimes it happens so slowly you don't even realize it's getting darker. It's harder to do some things, but you make adjustments. And you know this is only temporary. Tomorrow or the next day or maybe the next, there will be light again.
One day your spouse or a friend or a coworker points out that your room seems dark, seems like it's been dark for quite awhile now. This might suprise you. Perhaps you didn't notice how dark it was. Perhaps you didn't know that others might notice. You tell this person not to worry. You know all sorts of tricks to get the light brighter. You're working on it. It will be better soon.
Then one day you wake up and there is no light. You admonish yourself not to panic. You feel your way around the walls for the window, for the door. After the first lap around your room, you take a few more, slowing down each time, convinced you have just missed the way out, convinced you are not trapped.
But the dark eats at your confidence. Soon the panic and fear have their way with you, and you are trapped. Perhaps more surely trapped by these feelings than by the dark room. None of the tricks you have learned over the years will bring back the light. You suddenly know, know to your core, that there will never be light in this room again. You are lost.