All work and no play makes your sim a dull creature! If you just work non stop on learning how to cook, your sim is going to balk and insist you do something more enjoyable. This can be dancing to the stereo, reading a fun book, watching TV or all sorts of other things. Your best bet is to find something that is educational that your sim enjoys doing too. It's also great to find multi-people fun activities (playing chess, etc) so you get fun and social and logic improved all at once.

The Sims 2 Tips, Techniques and Walkthroughs