Fallen,

It's certainly not an uncommon feeling for you to not want to use your safe word. I've heard many subs say the same thing, that they feel like they've "failed" in some way. But you have to realized that the safe word is there to help both keep you safe, and your Dom learn where your limits are and more about your reactions. No matter the experience level, there will still be a learning period for everyone to adjust to the different limits of each individual. So, I'd encourage not to feel like it's a failure in using it, but rather a point in which you are helping you and your Dom to grow and get to know each other better. Of course, just my opinion. You might take a look at this thread, Safewords and Safesigns, to see that you aren't alone in this feeling and for some more information about it.

Cheers,
Myst