I have a few big losing one! Listening to my boss' trading recommendations... For example: buying the VIX in August at around 24% if I recall, in much bigger size than I usually allow myself to trade. Reminder to myself: keep investing the same amount as well as in instrument you are familiar with, I had promised myself in the past never to touch the VIX... I also listened to the tip of a friend on a Biotech stock that was supposed to get approval, and did not, but here I knew the risk so can't blame him - that's lottery ticket territory.
Biggest mistake though, holding my cryptos through the huge up run, and holding them through the huge down run, as well as holding 1/5th of my cryptos in a hot wallet called FTX (am still HODLing fully knowing that it is likely going to keep correcting)

For the CHF you are likely right in terms of direction of FX, but as I earn in CHF I tend to just accumulate with my salary and pension in CHF and do not mess too much with it nor FX it, also have a house asset in CHF. My savings are all GBP, USD, EUR and XAU and I play with this mainly - here my thinking is I want to stay diversified away from CHF as all my earnings are here now so my allocation naturally will grow to CHF with time. Also in USD I have a decent part in oil as well, so you could consider that a currency in a weird way, same as gold (XAU) (or Bitcoin!!)