Well, i can do it no matter how lit the room, as long as i don't stare directly into the light source. It really doesn't take much time to learn.
The trick is to look at nail or some other thing on the wall and it has to have a size so that you can't move your eyes "around" it. In other words, it needs to be so small that you can see all of it without "micro moving" your eyes.

And yea, give it a try.