Treated the valuation gap as an entry signal and got the timing badly wrong
This is a loss on process more than on money, and the process error is the interesting part.
Last year I built a deployment plan around the gap between public REIT valuations and where comparable private real estate was being marked. The gap was wide by any historical measure, the argument that it closes eventually is sound, and I've seen credible work calling this stretch the longest such divergence since the early 2000s. I read that, agreed with it, and then did something dumb with it. I treated a wide gap as a signal about when.
What I actually did: deployed 310k into a REIT sleeve in two large tranches about six weeks apart, weighted toward industrial and data centers, on the reasoning that the discount was extreme and therefore near its end. The sleeve then went down about 13 percent over the following five months and spent most of a year below my average cost. It has since recovered and I'm modestly ahead, so the money is fine. The plan was still wrong.
The specific error is that a valuation gap tells you about expected return over some long horizon and says nothing about the path. Two mechanisms can close it and they work on different clocks. Public prices can rise, which happens in weeks when sentiment turns. Private marks can fall, which happens over quarters because appraisals lag and nobody wants to write down a fund. When the second mechanism is doing more of the work, the gap narrows without your position going up at all. I had modeled convergence as a single event.
Second error, smaller but it cost real money. I sized the tranches off my conviction in the thesis rather than off my ability to keep buying. Two tranches six weeks apart is not a deployment schedule, it's one decision split in half. By month four I had nothing left to add with and the best prices of the whole period were sitting right there.
What I'd do differently. Deploy on a calendar over 12 to 18 months regardless of what the gap does, hold back at least a quarter of the allocation for a drawdown, and stop using the size of a mispricing as information about its duration. The thesis on convergence I still hold. My timing inference from it was unsupported.