I've given variations on this speech to way too many people this week (which needs to stop; things need to get better for everyone tout suite). In summary, with different points applying more to different people (including myself):
1. I'm really sorry things suck right now. It is not your fault. Thinking of what you should have done differently is not only unhelpful, it's unfair to yourself. No one is all-perfect or omniscient. All you can do is deal with the situation the best you can moving forward.
2. You will deal with this. It may not seem like it now, but you will. Things will get better.
3. Worrying about the worst-case scenarios is unproductive and very hard on your body. As my mother points out, your body doesn't know the difference between what you're experiencing and what you're imagining experiencing. Stress can negatively affect your body in many, many ways.
4. Take time to take care of yourself. It will make you more productive and effective. Do something simple you enjoy, like read a book, go out with friends, garden, get a manicure, have a glass of splurgy wine, cuddle a pet, or play a game with your favorite kid.
5. Call me if you need anything.