I really want to comment here. I had been a very good day trader in the past (1995-2001s, 2009-2012s) but when I recently retired and decided to try again, I got slaughtered. Yes, I made many stupid mistakes, but these are "new mistakes" - things that used to work for me now worked against me.
Back when you had to pay for real-time quotes, back before HFT, back when spreads were fractions, I could make money. I was not a scalper but I could see trends and pick up on them. That could mean staying in 5 minutes, or five days, but I almost always got out with a profit. These days every trade I entered started going down immediately. I would SWEAR it was like someone was watching me and going against my trade to squeeze me until I had to get out or risk losing a ridiculous amount. 90% of the time4. I could buy a stock that had nothing but upticks for 2 hours and the moment my trade went through it would drop like a rock. Absolute truth.
Here are some of the things you should NOT do in the modern market. Do NOT trade big, keep your sizes to 100 shares or under 25k. Do NOT bail at the first sign of a loss (cut your losers), ride it out until it comes back up. Check long term charts and look for signs of resistance and support. But best advice: just don't do it. I would have been far better off just buying 20 stocks in small lots and not looking at my account more than once/month.
I am seriously considering writing the book "How Not to be a Day Trader." - it just does not work. Even the pros who used to work on the floor of the CME will tell you things are different in today's computerized market. Day trading does not work. The reasons are "HFT traders undercutting your fills", "Brokers selling your orders to market makers," and more. There are even theories out there of retail traders being out into different pools where the odds are stacked against them, where they see different prices than brokerage traders. I will say that it really feels like this is true when you are in it.
Anyway - the best way to make money in the market is to pick good companies, buy them on down days (market dips) and just hold on. Do not ever put all your funds into one company for a day and try to hit a homerun. Spread it out and just trim out the losers on a steady basis. The private investors who make money in the market are the people who build portfolios they plan to hold for decades. With splits, etc. you could find yourself making enough on dividends alone after 20 years not to have to worry about how much your stocks are going up.