 Leaving too much money in cash for too long, that is a guaranteed loss. If you've been listening to TV, you know inflation's over 5%, 6%. And if you're sitting in a money market getting .00 nothing, you're going in the hole. Inflation is killing you. So please, please, please do not leave so much money in cash for so long. Another one is just overthinking every decision to the point that you never make a decision at all.