What behaviors you wished you nipped in the bud?

Hi new parents, my LO is about 9 months old, and I'm starting to see his personality shine through. He's starting to crawl all over the house and we're having a blast following him around.

Early on, everything is cute, but I'm wondering what are behaviors you thought was cute early on but then in hindsight wished you had been more stern in correcting the behavior.

What do you think? Care to share some early lessons?