Do we know when the bottom is with foresight?
Just keep investing regularly as long as you still have a long time horizon, while staying diversified to manage risk exposures.
Over time your cost is the average price in a long term uptrend. As you are nearing the time you would need funds, and you can plan for an exit at a higher price than you paid for on average.
As we still value assets, including crypto, in dollars and it is the most abundant ever inflating medium of exchange, at the very least inflation will take care of the nominal price growth over time. In the context of crypto, as we continue to believe this is the future and there will still be growth and advancements, fundamentally day to day fluctuations are just noise when you "zoom out". And you can zoom out so long your time horizon is not measured in only a few years.