I understand. You’re off to a bad start; you need to begin by building your self-confidence: like self-control, for example.
Without self-confidence, everything else falls apart, and you’ll be more vulnerable.
Start with this basic but powerful mental exercise:
This basic exercise will help improve your concentration, memory, and everything else mentally. Naturally, as it should be.
You can design other physical exercises yourself; the one I gave you is just an example.
I won’t give you a manual or a book. On the real battlefield, you’ll lose if you follow manuals or set guidelines.
With these mental exercises, you have the essentials; you just need to start applying point 3 on your own.
For example: the one about WhatsApp and the mystery box is just an illustration. What would you do in a scenario like that if it were real?