I also believe I am guilty of creating a false reality in which I excel at everything I do.

Is it a false reality? Or is it that you are so focused on certain aspects of what you do (aspects at which you likely do excel), that sometimes you don't notice the parts in which you are deficient.

I myself tend to do this quite often, I find something I enjoy and then hyper-focus on it, sometimes to the detriment of other aspects of my $work/$play/@etc. Sure I do my best to not neglect the "not-so-fun" stuff, but it never really gets the attention it deserves. You only need to look in my leaf clogged rain gutters to see evidence of this ;)

I think though that this is a natural human tendency, and one which is probably not such a bad thing in our ever-expanding and ever more specialized world.

In truth, I only choose to do things which I am good at.

Of course you do, because there is a good chance that you enjoy doing those things which you are good at. I mean after all, if you didn't enjoy them (on some level, some "sicker" than others), then you would not have done them enough to get good at them. I see absolutely nothing wrong with this at all, in fact I think it is an admirable quality.

And from a practical business point of view, people who enjoy what they do make the best employees because the take pride in their work. In fact, my $boss considers it a requirement, more so than any type of college degree.