You will feel tired after a few four sector days involving early sign ons/late sign offs. However, after a good nights sleep and a lie in on your day off you will be pretty much back to normal.
Compare that sort of flying with arriving home in the morning after a fourteen hour flight and an eight hour time zone change. Crawl into bed totally stuffed, sleep for ten to twelve hours and wake up late in the evening just as everyone else is going to bed. Watch TV or read for a few hours and try to get back to sleep. Get up at lunch time the next day feeling groggy and spend the afternoon feeling lethargic but unable to sleep. Go to bed at the normal time but have difficulty getting to sleep and wake up several times during the night.
Repeat two or three times per month.
