The difficulty adjustment is a network declared value adjustment.

The price on the energy market (mining) goes up or down with the difficulty.

The price on the FIAT market seems unrelated but it isn't, as it is closely tied to the movements in the marginal costs of new coins.

If the difficulty regularly goes up, then the value is going up. If the price isn't going up but the difficulty is, then it's in a crash which is a good time to sell FIAT for Bitcoin and HODL.

If the price is going up FASTER than the difficulty is, then it's still a good time to acquire Bitcoin and HODL (with caution though, there is always a correction) but it's also a better time to use Bitcoin to pay for reasonable life expenses.

Avoid buying FIAT with Bitcoin if it's below it's mining average cost of production, instead just borrow FIAT to be able to continue to HODL while it's undervalued until it returns to a price that's above it's average mining cost, and avoid selling FIAT for Bitcoin if it's more than 3x it's mining average cost of production.

Don't trade, just buy HODL and sell based on whether coins are overvalued or undervalued relative to their production cost for miners. That's it.

The more people do this, the more the price will be anchored to it's marginal cost and the more stable it will grow to be able to be used as a global unit of account.