Still learning to say "No"

"Pease, Mommy! PEEEASSEEE!"

As a Mom of babies I've pretty much got things down. I can handle poopy diapers and manage my time fairly efficiently, but I'm definitely still learning as a Mom of a Toddler. Even though Cash is fairly good at communicating for 18 months, we are still going through the tantrums when he a) wants something and can't tell me what or b) wants something and asks and I say "no."

Saying NO is hard. I always explain why he can't have it, but there's only so much information he can take in and sometimes he just wants it regardless. One of the things he is ALWAYS asking for is his Sippy Cup. I've never seen a toddler down a bottle of juice so fast! They spoil his meals and are probably rotting his teeth, but sometimes its just so hard to say no. I still do, but sometimes I don't and I feel terrible. He can drink a whole bottle of juice and immediately asks for another. Most of the time I tell him no, but that's when the tantrums start. He doesn't understand why I just gave him one, yet when he wants another he can't have it.

I try to distract him, which works sometimes but not always and sometimes I'm just too tired and just give in.

I don't want to start him on a terrible bratty pattern of expecting to get everything he wants. I just want him to understand that one is enough. Boo.