But if you're not fully invested (at least to your target equity share, which generally shouldn't be 100%), when the market unexpectedly jumps higher, you miss on that end. It's a trade off and I'd rather just have my chosen money in the market and let it take care of itself. Market timing is for people who want to spend a lot of time watching the market.
I use automated triggers to do most of my trading. If I see the price is getting good on a quality item, I'll set a trigger to buy X number of shares when it hits Y price, then I'll set another trigger to sell it after it has went up to as high as I think it will get before it begins to sell off again. Sometimes its days, sometimes months. The trade triggers will stay in effect until you cancel them. Sometimes I don't set a trigger to sell it back at all, if its something I think I'd like to keep for years to come. Takes about 30 seconds to set up, and I'll get an email and text if any of them are triggered. No need to boil my blood pressure watching a screen full of numbers bounce around all day. I wouldn't last a month as a day-trader; I'd have an infarction of some kind watching those high frequency trading computers manipulate the short-term prices the way they do! LOL!