I watch my balance daily. I shouldn't, but I can't help it. Here's what helps for me:
1) Change your mindset. If you were stockpiling socks, not stocks, you would want the price while you're buying them to be as low as possible. Try to think of them as socks, not stocks. You're buying a commodity for the future. The lower the price you pay per unit, the better. Just keep buying them as the price drops. (This works best on index funds that will recover in time.)
2) Change your timeframe. Look at the charts on the 10 year timeframe or higher, only. All the short-term noise washes out. The long-term trend is easier to take. If I'm trying to invest on a long-term cycle, pay attention to that longer-term chart.
3) Change your metric. Track your total number of shares, not just the price. Remember, the more shares, the better. The lower the price goes (if you're dollar cost averaging), the faster the shares accumulate. If you stay the course and buy while the price is down, at some point in the future, you will be very, very happy. The pot is boiling. The number you want climbing is the number of shares owned.
4) Set a goal for which the balance is irrelevant. I've got my budget pushed to the point where we can meet our contribution numbers if we concentrate, but not if we spend willy-nilly. My goal is to keep the budget balanced and meet every contribution target this year. The only number that counts is that my contributed balance keeps climbing, and was on target in each pay period.
5) Predetermine your decision. Never sell in taxable. To buy in taxable is to hold it until retirement. If you have to rebalance, do that in the tax-deferred accounts. If I can get away with it, my ideal holding period is forever. Once you accept that, the decision is made. No sales. No panics. Prices dropping is part of the plan, because they have years to recover. If the FIRE plan doesn't work, it will still come close. I'll just work a few more years. I'll still be able to FIRE way before 65. By the way, this really works. Most people don't panic sell in their 401K retirement accounts. Generally they ignore them. They'll worry about it when they retire. Selling in taxable results in tax consequences. Therefore, don't sell.
6) Validate your strategy in portfolio visualizer. If it handled the worst situations that have occurred so far, it has a fair chance of handling future bad markets. Then I'm watching it play out.