What should investors do in a record-breaking environment for indexes? (2)

The situation looks pretty much in the last phase of the bullish cycles, when everyone says the market can grow to infinity, and buyers of the last "plan" become individual investors.
Think about it, would you shorten the S&P 500 index right now? Probably not ... And why? Because you shortened it most likely to 2,200 points, then again to 2,300, then to 2,400 and now to 2,500 you give up.
What, however, has changed to opt out? Generally speaking, you are tired and you have decided that there is no point in shortening the index anymore. And it is very possible, even if you start considering to buy it. For example, if it returns by 5%...
It may be good, and it may be a bad idea! Time will tell. History shows, however, that there are no endless cycles of growth without any corrections.