To be a successful investor, we must always be able to evaluate, most people think long term after buying because based on history that has happened, but in my opinion with evaluation we will always be able to get big profits even in a short time or less than a year.
I would believe that there are people who make money on day trading as well, so that is not a bad thing to try to guess and make money in a single year. However, the amount of money you could make on day trading for a whole year, is not on the same average as the person who makes a long term investment.
You can beat them this year, or maybe next too, but if you look at the next 5 to 10 years, while they will be making a lot of profit, you will be hoping to keep it going if you are not a great one. Surely, there are some amazing traders and you will make a great return but that doesn't change the fact that it is only a small amount of traders who are like that.