When to buy and when to sell actually seems simple, but the fact is that for trading, especially for day traders, things like this are not as simple as they say because it returns to the initial focus, as I said, there needs to be further learning and understanding if you really want to do that.
I agree, in day trading things get even more difficult to manage and micro-manage. Daily swings are unpredictable and hence I prefer to play it safer with long term trading and advice the same to newbies who are willing to play it safe as well. I do admire those who day trade and make a living out of it, but its not my thing, honestly.
I am not sure how much luck can actually help here because this ends up being a gamble everyday when it comes to day trading or short term trading. Quick decisions and a fast internet - all the more anxiety inducing. I am not sure everyone can handle that pressure.