If this is not just a writing exercise and you are suffering from this much anxiety, the question is how do you channel it. If it starts to affect your ability to leave the house, then it’s a real problem that requires professional help.
If it’s just an overactive mind that won’t let you sleep, start writing Steven King style horror fiction. You’ve got the ability to weave a good story. I really liked the whole bear thing. It starts innocently and spirals into a horrific, but darkly funny situation.
As the writer, you can use the same powers of imagination to visualize a different ending to your story. For example, just as the mountain lion is about to pounce, the bear throws the lion out of the way. You look up and see a bee hive within reach. Grabbing it, you throw it at the bear who gets distracted by the honey and starts eating it. Suddenly the bees arrive and attack the bear who runs away, while you make your escape.
Sports psychologists use visualization exercises in the same way to overcome performance anxieties for athletes. It’s difficult and it takes a lot of time, discipline and practice, but it works. I’ve done it.