Although I agree with you about learning to "estimate" being important, there's another very important thing that must come with it: learning not to trust them.

From my small experience, even better than estimating something right, was having the humility not to trust blindly our own instincts.

Don't get me wrong, one has to listen to her own "guts" many times in a life, and that's a good thing. A better thing is learning to recognize when you screwed up, and getting yourself out of that situation before it is too late.