Repeating mistakes sucks. I probably wouldn't even have realized I was doing it, except for the vacation I just took. Guess that just proves the value of keeping your head clear, especially for people who do more thinking/decision-making and less athletics.

My mistake: trying to build when I should buy. I thought we could get something done more cheaply with in-house staff, but it's not going to work. We need to hire a vendor.

Professional builders (of software, organizations, etc) fall into that trap way too often: wasting a bunch of time trying to replicate what's easily available off the shelf—available now, and with far less risk. I think the root cause is pathological optimism: refusing to accept that something isn't possible (doing a better job in-house), even when it's not likely.

I'm in good company; the following is from Paul Graham (Relentlessly Resourceful):

I'd almost say to most people, but I realize (a) I have no idea what most people are like, and (b) I'm pathologically optimistic about people's ability to change.

From a different essay:

I flew into the Bay Area a few days ago. I notice this every time I fly over the Valley: somehow you can sense something is going on. Obviously you can sense prosperity in how well kept a place looks. But there are different kinds of prosperity. Silicon Valley doesn't look like Boston, or New York, or LA, or DC. I tried asking myself what word I'd use to describe the feeling the Valley radiated, and the word that came to mind was optimism.

—Why Startup Hubs Work (also pg)

Ben Thompson says this Polyannish Assumption is why facebook failed to anticipate the Cambridge Analytical scandal. Not sure that's 100% of the story but it seems plausible (good read).

I'm just trying to stay aware of it. Yet again, from Paul Graham (emphasis mine):

This is isomorphic to the principle that you should prevent your beliefs about how things are from being contaminated by how you wish they were. Most people let them mix pretty promiscuously. The continuing popularity of religion is the most visible index of that.

I'm not sure the sleight against religion is quite fair; optimism is just as much a religion as, say, Judaism: something many follow even if it's not, strictly speaking, "accurate". I'm sure Jonathan Haidt would have a lot of insightful comments about the comparison.

Related: Auren Hoffman's answer to "What are the most important business skills?" Vendor management: The most important business skill in the next hundred years is the ability to select and manage vendors.