Dreamcatchers were originally intended by the Iroquois to keep a sleeping person’s good dreams and let his bad dreams pass through. In fact what happens in dreams is that we lose our identity; we become another person, another “soul.” That’s what has to be “caught” or prevented.
When I doze off in my recliner I enter a new world and take on a new identity; it becomes a new umwelt and the old one disappears. Fear of that must be one reason I have trouble sleeping. If I didn’t have that fear I could become a good Epicurean or Buddhist monk of the Hinayana sort; one disappears and becomes satisfied with the new identity.
As it is, I look forward to what will happen and regret what has happened in the past. Spinoza comes into the picture here because to him regret is a weakness, a loss of our power or virtue (in the classic sense of the term).
In point of biological fact, we simply respond to whatever the moment brings as if it were the only reality. That is what we must learn to control.