My mistake last year was to invest in $ProShares UltraPro Short QQQ(SQQQ)$ and tried to DCA as it falls. In the end, I had to sell to prevent further loss. This year, plan to invest on good quality companies mainly those with big caps and also try luck to invest in some crypto related investments.
Biggest win is $Amazon.com(AMZN)$ bought it due to the potential growth of AWS and AI adoption. Most challenging investment is $Advanced Micro Devices(AMD)$, did not expect it to go so low, waiting for chance to DCA to lower the average cost.