I was 19 in 1999 and just started investing. All of my portfolio was in tech. I made a killing until 2001. I was not aware of any other sector at the time, so I got killed with the .com crash. That was an expensive lesson I learned, also it’s only several k, it was a lot for a 20 year old. I did more research after the crash and learned my lesson. Now, I keep an eye on all sectors. You don’t have to do day trading to make money in a down market, you just have to know which sector to be in at any point in time. After all, I’m still learning and perfecting my skills as life give me more lesson.