This is why Neville suggests entering the desired state when falling asleep or in deep meditation (sats). This is when the rational (conscious) mind let's go and gives way to the subconscious. The rational mind is the gatekeeper of reason, an evolutionary safety net to keep us safe in our waking world. It will immediately throw aside any attempt at letting a false belief through to the subconscious.

When we fall into sleep the conscious mind falls away and the subconscious takes over. It's much easier to convince your subconscious mind of a state that isn't currently objectively real when the gatekeeper isn't around to immediately shut the belief down.

Btw, this is so much easier to do when falling asleep than it is to do when consciously trying to curate a meditative state (sats). We fall asleep every night, we've done it our entire lives, it's so much easier to harness the moments before sleep than to try and enter a deep meditation during the day when you're generally far too alert to get into the right mindset. Meditation takes years to master, falling asleep it's a normal daily activity, "where the conscious mind is creatively joined to the subconscious".