In this case:
char *str = "Sometimes I feel like I'm going crazy.";
You’re initializing str to contain the address of the given string literal. You’re not actually dereferencing anything at this point.
This is also fine:
char *str;
str = "Sometimes I feel like I'm going crazy.";
Because you’re assigning to str and not actually dereferencing it.
This is a problem:
int *pt;
*pt = 606;
Because pt is not initialized and then it is dereferenced.
You also can’t do this for the same reason (plus the types don’t match):
*pt= &myVariable;
But you can do this:
pt= &myVariable;
After which you can freely use *pt.