Don't eat ice. Ever.
Oh and no Grape-Nuts. That used to be my favorite cereal, too.
Your mouth will stop feeling like it's huge and swollen in oh, a few months, lol.
Take very good care of your gums. The healthier your gums are, the less discomfort you will feel. Also, if you don't care for your gums properly, it will delay the removal of the braces when the time comes, even if your teeth are perfectly straight.