Defensive Programming

I used to be a student of the ``Defensive Programming'' school of programming. I'm mainly a C programmer, but I occasionally dabble in languages such as LISP. Anyways, whenever I would program in C, I would program very defensively, and check that all the arguments passed to every function were not NULL (assuming they were pointers. This turned my code into mostly a bunch of if statements.

After a while, I figured out that this was pointless, and most of the functions I write today, I don't bother checking if the arguments are NULL or not, because only a smart fucker such as myself is going to be using them. I instinctively know when everything is NULL or not. Of course, I do still check the arguments sometimes, but definitely not in every function. It just turns into a mess.

What do you guys do? Am I a retard, or are you similar?