It's really hard to do MPT on your own. I got really into finding a collection of 10-12 mutual funds that are in a collection of sectors. I also mixed it with a strategy of selling each fund when it went below its 12-month moving average, and buying back in when it went above. I backtested it a bit and read some studies and it seemed reasonable. Sacrifice a little upside to protect against more downside. It sure would have saved me had I followed those strategies during the last two mega crashes; the dotcom bomb and the finsys crash.
Of course, since doing that, the S&P has been on a sustained climb that I've only partially benefitted from since I've had some bond funds, etc. The selling/buying has worked ok - it's whipsawed me in some cases and saved me in others, but given that I'm not spending more than a day a month on it, and that I only have a surface level understanding of sector-balancing, and that while it seems my funds are cheap, who really knows for sure... I'm regularly tempted to just dump the whole thing and get back into one fund, just in time for the next crash the other part of my brain says.
Also, it's worth pointing out that a lot of the "beat the market" talk is rubbish for entirely different reasons. People tend to get more cash to invest when times are good, and less when times are bad. That means that the average person is going to buy more when the market is high, and less when the market is low. I don't ever see this accounted for in studies. Even if you were to drop your money in an S&P-500 index fund whenever that money becomes available to you, you're still going to underperform the S&P-500 long-term by a moderate amount.
Of course, since doing that, the S&P has been on a sustained climb that I've only partially benefitted from since I've had some bond funds, etc. The selling/buying has worked ok - it's whipsawed me in some cases and saved me in others, but given that I'm not spending more than a day a month on it, and that I only have a surface level understanding of sector-balancing, and that while it seems my funds are cheap, who really knows for sure... I'm regularly tempted to just dump the whole thing and get back into one fund, just in time for the next crash the other part of my brain says.
Also, it's worth pointing out that a lot of the "beat the market" talk is rubbish for entirely different reasons. People tend to get more cash to invest when times are good, and less when times are bad. That means that the average person is going to buy more when the market is high, and less when the market is low. I don't ever see this accounted for in studies. Even if you were to drop your money in an S&P-500 index fund whenever that money becomes available to you, you're still going to underperform the S&P-500 long-term by a moderate amount.