My experience, short term trading is counterproductive for the following reasons.
The best moves and opportunities happen (seen after the fact) by the least obvious signals.
Breaking this down: Volume as an example which I've studied alot, often gives conflicting signals. You can have good price moves on both low and high volume.
Price breakouts and breakdown can move at any time with no warning.
What I've experienced time and again, the mkt always does what is least expected. I've repeated this phrase numerous times on ET.
If you are not in a trade, one cannot profit from it.
If you chase a trade, often it pulls back and then what to do? Hold? Thats not day trading. Sell? Ya for a loss!
For all the decades of my trading, I still cannot predict a move, all I can do is work on probabilities and those probabilities take time to form.
Day trading is good if you want to burn energy.