Whatever you do, don't jump out at the bottom! You have to hold on and ride it out. However, it is prudent to reduce exposure a bit when volatility is too high. See "Kelly Criterion" for how to calculate this. Inverse volatility weighting is usually sensible for this reason.
You can guard against left tail risk with insurance. See the VXTH index and the SWAN ETF for good strategies here. Don't buy too much insurance, or you can't make money.
You can also think of your future salary as a kind of bond in your portfolio that you can't sell. Seen in that light, the optimal balance is probably using some leverage, even if that means risking a total wipeout early on in your career.
Don't try to figure out when the dip will occur, just sitting with cash on the sidelines in the meantime. Buying a little every month is generally the best strategy most of us should use:
If you're saving for retirement, then you actually want it to go down (occasionally): that means your monthly contribution can buy more for that month. Then once you're near retirement you move your portfolio to something more a conservative leaning so the swings don't effect you as much.
For that to play out: are you planning one doing one enormous index fund purchase and never investing again?
If you’re talking IRA, we’ll you could have only put in $6k. Market dumps and the following year you can put in another $6k at a much lower price per share.
But what if I buy before a bear period? I will be stuck there 10 years just to recover my money and another 10 years to make some returns.