I'm similar to you in terms of age and finances.There was a thread a while back where we discussed the merits of "Once you've one the game, quit playing" and I agree with this approach. It turns out that being risky once you've made it typically brings little additional gain but plenty of risk.
Along those lines, one thing that's helped me greatly is to invest in safe (but low return) assets the amount needed to cover basic living expenses, factoring in all other safe sources of income you may receive such as social security or pensions. The rest is invested in stocks, real estate, etc. So, no matter what happens in the markets, I know I'll always have enough to live comfortably for the rest of my life. In all likelihood, though, the money invested more aggressively will gain over time (duh) and I'll end up with more than I need (which is proving true already despite flat markets as of late).
Simple Example: Say a comfortable lifestyle for you is $4,000 month, but $3000/month (adjusted each year to inflation) will at least cover basic living expenses. You conservatively guess you might live to age 83 (40 more years for you); Social Security at age 63 will equal $2000/month. You have 20 years to cover until you start drawing Soc. Sec. Therefore, you'd need from your own assets
($36,000 times 20 years = $720,000)
+
($12,000 times 20 years = $240,000)
= $960,000 to cover you for the rest of your life. That amount you'd invest in something like government securities and safe bonds that will not suffer during market swings. The rest of your $1.4M, or $440,000, you can invest in stocks, real estate, whatever and withdraw as you want so that you don't have to just meet "basic" living expenses. In my case the safe haven is the "G Fund" in my Thrift Savings Plan (federal government version of a 401k) that reliably returns about 2-5% annually and can never go down.
I've only been FIRE'd for a couple of years starting at age 47, but this helps me sleep at night knowing I don't need to be concerned at all with market ups and downs. Even if it ends up not being the absolutely most optimal in terms of eventual returns, I don't care. It's more than enough, and as it turns out the difference in gains between conservative and aggressive allocations is marginal or nonexistent. Lots of research shows that relatively conservative asset allocations end up performing nearly as well as aggressive allocations, but with far less volatility and risk.
Another side benefit of this approach is that because I know my basic expenses will always be covered by the safe investments, any gains in the other investments are mine to withdraw and use as I please whenever I want -- I don't need to keep it in reserve to cover future down markets (an ever-present concern with straight SWR withdrawals, i.e., "Will my portfolio last??"). It's been nice knowing I can afford an extra trip or to buy something I want without wondering, "Should I have preserved this money in case I can't meet expenses down the line after a really bad and long market downturn?"