I have terrible difficulty in avoiding errors in gender agreement. It isn't just the "puzzling" cases, such as masculine words that end in -a (el planeta, el tema, el mapa), or the feminine words that end in -o (la mano), or the feminine words that end in -a but take <em>el</em> anyway (el agua, el aguilla). It's that I just can't make it automatic. The part of my brain that is capable of automatic, fluent speech just doesn't accept the idea of gender.