Fascinating.... someone also posted a study re if you didn't hold overnight you'd have missed most of the upside in the s&p during it's run up, supports the graph
So just buy and hold, except ..... unless you hold forever there is always the little bugaboo of timing. Which actually is all there is to profiting short or long term.
This is true -- yet folks still don't want to hold because of "overnight risk." If you know how to read the market, this is key. It's a lot less stressful and you're essentially making money while you sleep instead of stressing while looking at your screens during the day. Larry Williams and Linda Raschke have been overnight holders. I'm not saying you have to sell the open, but holding overnight is a key to bigger profits.
Manage your risk accordingly. Now with the micro index futures everyone should be able to hold 1 contract overnight. If you can't manage that, you should stop right now and save more capital.
Here is a NY Times article from 2018 on this subject. https://www.nytimes.com/2018/02/02/your-money/stock-market-after-hours-trading.html