You are right because when you do trading (especially day trading), you always give a hard couple of hours to stay in your computer looking and monitoring the price movements of cryptos you wanted to trade. Not only it will affect your eyes vision, but it can also affect your portfolio's health too when you make wrong trading decision.
Well, when it comes to day trading, you necessarily does not have to stay the whole day on your system as you can still end up making some substantial profit and close for the day without having to stress yourself. I used to day trade, but had to go the long term way as a result of time and my new job.
You do not need all the hours, just take your time, look for a pattern and a setup, trade that set up, make your profit based on your strategy and close your PC for the day. The problem with a lot of people is that they want to day trade and make all the available profit within that day, and this is one of the reasons why so many of them usually end up flopping eventually.