Training is number one. Mitochondria this and slow twich fiber that. I don't even know what the hell he's talking about half the time. But the guy doesn't train. Better to do something even if it's wrong than to know everything and not practice anything.
Recovery is two.
You will regress and maybe get injured without it. Mental attitude is three. You can't lift a weight you are afraid of. There are a bunch of tricks and techniques to build confidence. That is an article in itself.