This always seems like it'll last forever while it's happening, but it never does. Double down, triple down. If business is ridiculously good lately, pour the time in to max out the current opportunities before they (likely) fade away. Bank cash, etc.
The same goes for creativity. When you're having a highly creative day, run it out as much as you can. Resist the temptation to say, "Well, that's enough" and just go chill out or whatever. Max inspired time is rare. Milk that cow when you're max inspired.
During bad times, re-double on fundamentals and try to avoid doing anything stupid. Fundamentals keeps you from hitting the vicious downward spiral. Super basic stuff. Decent sleep schedule, eat well, drink enough water, time in nature, time socializing with people you like. If things start getting hairy, really knuckle down on the most very basic stuff. That helps fight off the downward spiral.
And then try not to do anything stupid. Don't spend a lot of money or make irreversible decisions if your judgment is faulty. Just keep gearing down on fundamentals. When you're low creatively, this is a great time to do tedious consolidation. Clean the kitchen, clean all your gear up, clean up the files on your computer, get taxes and licenses or whatever filed and renewed, deal with bureaucracy and nonsense—this will free up your time to milk the cow more when you're max creative. Okay, this is my new plan. Normal life during normal times. Milk the cow as much as possible when things are unusually great. Fundamentals and trying to avoid being stupid when things are bad.
If you do those seven things—eat well, drink water, sleep on schedule, plan tomorrow before sleeping, start on what's most important, exercise, fully relax regularly, and get some time in nature—that almost guarantees busting out of a slump. If you're in a slump, you're almost certainly not doing one of those.
Ikigai by Sebastian Marshall