My approach is to try to ignore dollar-value (fiat-value in general).
Your wording makes it sound to me that you are worrying about the fiat value rather than focusing on the value-in-bitcoins.
If you take the position, which seems to me an extremely reasonable position, that fiat is actually basically yet another shitcoin, and look at its history which as far as I am aware is for every fiat on the planet that it goes forever downwards in value, often "by design", then...
...Don't worry about fiat's occasional "pumps", in fact probably tell yourself, when you see fiat "pumping", that it is almost certainly a mere "pump and dump".
Don't bother having fiat as either side of any of your trading-pairs.
I admit that since I earn my living via crypto I do sell off bitcoin or stellar lumens for fiat.
It is only very recently though that I am starting to toy with the idea of actually "trading" on the bitcoin/fiat and lumens/fiat markets, and that only as a ploy that I hope might boost slightly my eventual outputs of fiat to live on. A little boost on the way out, basically, so that when or if bitcoin or lumens tank relative to fiat I have a column of buy offers sitting there waiting so the dumpers dumping the bitcoin or lumen are selling them to me cheaper and cheaper and cheaper the more they "dump" and when or if bitcoin or stellar trends toward the moon I already have a column of sell offers in place so as it shoots higher and higher it is being bought from me at higher and higher and higher prices than I had normally been expecting.
Try looking not at how fiat is doing versus crypto but, rather, how various other cryptos are doing versus bitcoin, and build columns of sell offers going up and up and up and up, and columns of buy offers going down and down and down, so that whether bitcoin tanks relative to the other side of your pair or the other side tanks relative to bitcoin you are profiting on the other side of the pair; that way volatility is actually good for you too, you will find that coins whose price hardly moves are not very appealing...
But since fiat can pretty much inevitably be expected to go forever down in value, be very cautious about having any fiat as any side of any of your trading-pairs!
-MarkM-