One common thing you notice among highly creative people is how they completely lock down certain aspects of their life. It is as if they want to conserve all their mental energies for their creative efforts without wasting anything on miscellenous tasks. Hence you find people working with a single type of pens, clothes, walking routines etc.

So, not sure about Woody Allen's diet preferences but it seems to me that just taking out the option of eating unhealthy dramatically cuts down on decisions making and mental energy. A single Frankfurter will not alter your health, but if you open up the possibility of eating them you need to wonder - Is one per day OK? what about one per week? If you eat a hamburger does that mean you can't eat a Frankfurter for two days etc. etc.. If Allen is half as neurotic as he seems you can imagine him spending a lot of time deciding what to eat and what not. Just nukeing the option -- will not eat frankfurters, period. -- seems to be a good mental hack.