I have made plenty in my life, and some I've had to make more than once before learning the lesson. Unfortunately, those learnings don't prevent one from making brand new mistakes.
I'm horribly embarrassed to admit that I f***ed things up with FWB. Just when it was all going so well...
On New Year's Eve, by the end of the evening, I had had several drinks. I wasn't so drunk that I got sick, but apparently I said some things that were to be kept in confidence to one of FWB's friends. FWB is furious and completely [and justifiably] disappointed with me. I don't remember the conversation, but no matter -- the damage is done.
And I have no one but myself to blame.