There is only one thing certain in life and that is change. Whatever your current situation - be it GREAT or BAD or PRECARIOUS or SCARY, it will, most certainly, change. The understanding of that simple fact may just be the most important lesson we, as humans, could ever possibly learn. The trick is to remember it.
Life is cyclical. What is good will, eventually, get to be not so good. What is bad will always get better. When you are at the top of the world, there is only one way to go - down. When you are in at the bottom of the pit, the only possibility is to go up.
That can, of course, be depressing (except that it's really hard to be depressed when all is going well), or it can be wholly encouraging. And that is the perspective we must always take. Enjoy the good times in life. Make the most of them. Capitalize on your good fortune. Be thankful. Those good times will not last - but for now, enjoy!
If things aren't going so well, don't jump off a bridge just yet. They may, indeed, get a bit worse before they get better, but the better times are most surely on the agenda. Don't throw in the towel too soon. KNOW that, when you reach bottom, things have to get better. It's just a fact of life.