What are some proverbs/sayings about something small turning into something big, spiraling out of control, like a snowball effect?

Looking especially for Greek proverbs but they don’t have to be. Everything I’ve found is positive (something bad turning into something good) but I want it to be about a small thing that you do and brush off that later leads to enormous consequences (kind of like an unhealthy addiction)
Answers

Anonymous

Don't let very small sins turn into very bad habits. ~Saint Teresa of Avila Interesting how the saint considered bad habits to be worse than sins. But she always was a bit of a rebel.

Mike

Just remember that the mighty oak was once a nut like you.

Anonymous

Oh no, I am so constipated right now?