I still think it's more about the ESTps mood swings than advising about how to pick friends. I honestly don't think I ever give advice on the latter (maybe if asked, okay, but it's not that this situation comes up a lot usually.).

Also the making duality work article mentions this specifically: "Despite these natural inclinations, many members of this type are not even aware of their enormous potential and often suffer from lack of confidence, or hold some irrational notions. They need a partner who demonstrates inexhaustible optimism and faith in the success of any endeavor. The main thing is to rid these people of their anxieties, suspicions and doubts – the rest they will overcome themselves."