I'm not fond of heights. I'm not paralyzed by fear, but I find myself avoiding high places in normal (non-hiking) life. But on Whitney, which I day-climbed in August 2001 for the first time, I found that heights presented no problem at all. Perhaps my reason is idiosyncratic, but the main reason was that by the time I reached anything that presented a potential problem (generally, anything above Trail Camp), I was so utterly exhausted that I couldn't have cared less. I recall passing by the "windows" without so much as a quiver of fear. In fact, I didn't realize that they were the infamous "windows" until I'd already passed them by. Strangely, it was only after I finished the climb, and sometimes in the middle of the night in a cold sweat, that I've worried about the switchbacks and the "windows." But when you're there, it's fine. Don't worry about it.