post SHTF is not the time to start trusting strangers.
I trust no one now and in SHTF that goes 10 fold.
I have a lot of training in human behavior. I also have a lot of experience in reading body language both human and animal. I don't believe what someone is saying until everything jibes. Everyone, even psychopaths, have a give. I am pretty good at finding that give, often before they even open their mouths.
Thusly, I have a handful of people who I trust out of a lifetime of social interactions. I can do the loner thing as well but, I don't fight to survive for myself. I am already dead.
Many years ago, remember someone from the military, talking about military psychological training. They said what they do is teach you that you are already dead.
It seems counterintuitive. Why would they do they do that? Because fear of death is the main reason a soldier makes bad, emotional and irrational decisions that often, not only kill them but, many of their brethren.
If you have already accepted that you are dead, then psychologically, it takes that fear induced and panicked behavior off the table, clearing the way for rational thought even in the worst situations. Being dead, keeps you alive.
I have no fear for myself.