Pre-production is easy. You're in it now. You know, you've got numerous projects in various stages of development but don't have a penny to write a check. Now you quickly get everyone together and spend nine to eighteen days of 14-18 hours each, shooting from dawn to dusk. Pre-production is easy.
Production is a ball buster.
During Production everything happens at once. The actors, lights, camera, props, schedule, film stock, egos, temper tantrums, and all the rest. Production, although typically presented as being fun and joyous, will probably be the worst 2 or 3 weeks of your life. But you persevere. Somehow you get that Martini Shot.