Here's a problem that I'm sure every martial artist has had at some point...we think, more specifically, we tend to over-think. If you don't believe me, tell me if this sounds familiar: you're in class working with a partner doing something like point sparring, bunkai, self-defense applications, etc., and numerous types of techniques/applications are running through your head (example: "I can hit him with a round kick to the chest" or "If she does throws that backfist again, I'm cutting her off with my side kick."). By the time you've thought about it and decided what you're going to do, your partner's already hit you once or twice (or more....).
The three main things I tend to tell people that seasoned martial artists can learn from beginners (yes, we learn as much-if not more-from teaching as well as being taught) are open-mindedness, excitement, and plain common sense. What I mean by that last one is that, for the most part, anyone without any martial arts training would, in a self-defense situation, tend to do what comes natural and do whatever simplistic technique(s) necessary to end the conflict. Granted, there have been many instances in which a novice may freeze up when attacked, but there are just as many instances in which they have been able to defend themselves by simply doing what comes natural. Instead of thinking about which elaborate joint lock/manipulation you can do if someone grabs you, simply stomping on one's foot may be enough to suffice. Of course, common sense would dictate that not allowing yourself to be grabbed in the first place would be best!
*A quick point to point-sparrers* There's a reason that the great fighters in history teach the basic techniques such as the front, side and round kick day in and day out. While there's nothing wrong with experimenting with more elaborate kicks such as crescent and spinning kicks, the basic kicks are not only easier to pull off, but many of the more complex kicks are based on them.