The way to bridge that gap is to only volunteer predictions when you're quite confident, and otherwise stay quiet, change the subject, or murmur a polite assent. You're absolutely right that explicitly declaring a 65% confidence estimate will make you look indecisive -- but people aren't likely to notice that you make predictions less often than other people -- they'll be too focused on how when you do make predictions, you have an uncanny tendency to be correct...and also that you're pleasantly modest and demure, too.