One of my biggest accomplishments this past week was when, in the middle of responding to something with an "I don't know" or some version of it, I stopped and said "Actually, I do know" and gave my answer. Saying "I don't know" is often quicker and easier, especially since somebody else typically knows the answer (at least where I work they do). I'm not likely to correct somebody when they are wrong either - unless it is going to greatly affect them in the near future. I grew up as a smart kid in a mostly uneducated family - and have played dumb for much of my life. I was put down a lot by extended family when I spoke up about anything or showed any talents off - and learned that it was best not to talk about it - because nobody cared anyway. (I say extended family for a reason, my close family are the most supportive loving people I could ask for).
I don't mean to imply that I always have the answer, though. I also find the ability to say "I don't know" extremely empowering. I have no fear about saying it when I don't know the answer to something or don't think I can provide a good enough explanation. When you don't know the answer to something it is important to say that. Your ego is capable of giving a lot of misinformation, which isn't fair to the recipient.
Saying "I don't know" to something you do know - is a disservice to you AND the recipient. And for me it is full of fear of being wrong, fear of speaking up, and fear of engaging in intelligent conversation with people who are smarter than me (which alienates A LOT of people). I'm afraid of every possible outcome of giving a firm answer. I've learned, though, that playing dumb eventually means you aren't included in the conversation. People won't know you are smart if you don't let them know you are smart (duh!).
So, as I commit myself to "30 days of blogging, or whatever," I also make a commitment to stop playing dumb - even though I could win an Oscar for how well I play that role. Cuz' this aint the academy awards. This is my life.