This is perhaps the biggest irony of cooking. That the cook seldom has the appetite to eat what he has just prepared. The more difficult, prolonged or meticulous the cooking, the lesser is the appetite. This is the cook’s curse of selfless selfishness.
Nevertheless, professional chefs need to believe in the power of tasting during the cooking process as often as is needed or is possible. Something as simple as a plate of pasta can taste completely different even when made by the same cook during the same night. The difference between a good dish and a great one could be just a pinch of salt. So it's important to taste, taste, and yes you guessed it, taste again.