Misunderstandings are a silly thing to make yourself feel bad over. It's the intention behind your words that matters, and any sensible person understands that. Feeling bad about it doesn't do you or them any good, so just accept what happened, and commit to changing the source of the misunderstanding.
On that note...
Believe it or not, I tend to be a really crappy friend to a lot of people, especially when it comes to maintaining contact. Despite genuinely enjoying their company, and being ready to help them whenever they seem to need it, something as simple as initiating contact, calling people on the phone, writing a letter, or so on has always been difficult for me. When I look back and realize it, I tend to get upset that I hadn't kept in touch better. Still, I realize that it's of far more use to me and my friends that I make efforts to reach out more, rather than just feeling bad.
On a tangentially related note, I've always despise asking for help from friends and family. I feel like I should keep the burden of my problems to myself, and resolve them on my own, without outside aid. Part of this is wanting to feel capable and self-sufficient, and the other part is avoiding admitting my own fault and weakness where it matters. Much as regret and embarrassment makes it harder to contact friends and family the longer it's been between our conversations, it's harder to ask for help the longer I've been digging myself a hole out of stubborn independence.
All in all, the past week and a half has taught me a lot about not letting embarrassment, regret, shame, and pride keep me from doing what is best, and I have my friends and family to thank for helping me learn that lesson.