I think you're being hard on yourself.
1) as pointed out, you didn't lose your entire investment in the beef, just the delta in cost between what you got vs what you could have bought else where. (And add in stuff you might never have bought, if you got say the tongue.)
2) you really can't even count the investment that failed. The reason that stocks generally return more than risk free investments is...risk. You are taking on risk with any stock investment, including our beloved low cost ETFs. So, three things minimize your loss here. First, it was a learning experience. Almost none of us should be trading individual stocks. Dabbling as a hobby is one thing, but unless you have significant time to invest you're rarely going to beat the indicies. Second, you do get the capital loss, so that saves you 20% or so. Third, it really was just some risk coming to fruition.
3) Dog. Oh, I can so relate. Our rescued mutt has had literally thousands in training, including two 2 week stints at a "board and train." We haven't returned ours yet, so it's more of a "sunk cost" than a "loss" for us, but every time I look at our spending and see the "Pet" category I shake my head. It's ridiculous.