ng1: indeed, so what? ng2: huh? ng3: what? ng4: yeah, yes. ng~: nooo.
> There are several exceptions: in Greece, Iran, Turkey, Bulgaria,[2] Albania, and Sicily a single nod of the head up (not down) indicates a "no".
Though for Bulgaria at least it seems it's shifting with many people who lived abroad at some point(myself included) and have picked up the correct/more universal form. Which makes it worse: Now no one really knows whether you mean yes or no...
You can probably make yourself do it by saying out loud: "When I was young, I thought I understood everything." It's like an ongoing disagreement.