Eh, Whimsical, don't let these guys get you down. Seriously, I'm a complete TARD when it comes to Se, which is why sports class was an absolute nightmare and I thanked my lucky stars that I did not have sports class in high school.
I also notice this when someone says something unexpected and I'm like a deer in headlights and think of all the brilliant things I could have said after the fact.
It seems like an obvious answer, but the best way is simply to practice due to exposure. Teaching has helped me deal with the unexpected, for example, but I think I have handled that by training my Ne to deal with it.
E.g. someone asks me some random thing. Brain goes into active mode thinking of possible explanations and reactions in a fraction of a second, a natural mode for me. Se dom would come right out and blurt something, and so do I, but we come from different points.
So what I mean is, you let your other strengths compensate for your weakness until you get enough practice to develop it.
In addition, it helps to hang out with people who possess the strengths you desire. For example, my husband has a much more strongly developed Se than I have. So what ends up happening is that we go for a walk, I'm daydreaming about crazy stuff, and he'll say, "Hey, look at that bird," or "Did you see him?" That kind of thing wakes me up. At first I'll be like "Huh, heh, uh, what...???" And then after a while I start noticing things around me by myself. Seriously, I used to not even notice the seasons changing until one day it was like BAM, holy crap, it's summer - how the hell did that happen??? Now, I tell my husband stuff like, "Look at the beautiful leaves changing." It's a gradual process, but if you always hang out with Se-tards you'll never get there.
Hope this helps.