I try to keep things in check..and have done worse things with BTC this year..but the one that stands out as an OUCH!
Is the 1.01 BTC I paid when BTC was worth about $1,150 bucks...thus I paid at $18,920.73 btc now $19,109.94 to pour cement in an old
cistern in my basement to level the floor up....for a workshop there....again OUCH!
I did worse, last year...but reminded every time I sweep the workshop floor. Ack!
I paid 19 btc if I remember correctly in 2013 (currently over $350k) for a brick from Butterfly Labs.

Ouch, that's gotta hurt.
It's kinda interesting looking through posts from the past few years and seeing the same type of comments.
I think in the next 4-5 years, comments are going to be even more amusing to read. Instead of people talking about how they regret spending their btc, we'll look back 5 years from now and see comments like: "In 2017 I divested some portion of my bitcoin into multiple altcoins.... now I look back and did the math, and had I just left everything in bitcoin I would have had [2X/ 3X /4X /insert some multiple here] more wealth than I do now."
If I had left everything in Bitcoin THIS YEAR I would have made more money than any of my other Altcoin "investments" + trading (where I lost even more money because of high risk). Lesson learned: Never take advice from boneheads. Especially not in the crypto world.
But I think it's really unhealthy to think that way because the moment you make a decision that information is not available to you so beating yourself up for it later is really just as stupid. Just learn from mistakes and move on.