Heart Indicators

Well, I decided to finish this post; it's been marked draft for a couple months.

Situation: Something just happened that really bothered me.
Time: Any time.
My Reaction: I bite my tongue (or try some other innocuous response).

Why is it that when I'm frustrated, the first words that come to mind are ones which I've never said (and pray I'll never say)? Why don't any other words or phrases, ones which I've said many other times, leap to the forefront of my mind?

For some time, I was perplexed by this question. Something would happen (say, for instance that I dropped something I was carrying), and my responses would come in something like the following order:
1. I'd nearly swear
2. I'd stop myself and breathe some other word of frustration
3. Realizing what I'd almost said, I'd think "Why, Lord? How did I almost say that? I'd never use words like that!"

Once again, Scripture speaks to the issue: "The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks" (Luke 6:45). Contrary to what I'd like to think, it's not that my mouth nearly makes an inaccurate reflection on my righteous self; it's that my mouth nearly makes an accurate reflection on my sinful and self-righteous self. Next time this happens, I don't want to merely pray "Lord, help me to guard my mouth," but also "Lord, change my heart."

I'd be curious to learn whether anyone else has the same struggle, and if so, what they've learned through it. Thoughts anyone?