Now that's a great question!
Lets look at the job, you put passengers on-board that depend on your expertise, your ability. You load on many thousand of pounds of fuel, you start the engines running at 500-600 deg C, sitting under the fuel tanks! You hope MX did there job right. You climb to cruise, and travel at 85% of the speed of sound, many miles up! You can't breath the air, or survive at cruise, to thin and to cold. You fly a six day trip back and forth across the Atlantic, crossing over 20 time zones, after awhile that starts to hit you. You land in Narita (NRT) after 14 hours, and some passenger has a wise crack, as they exit the aircraft, about being 10 minutes late.
You spend many nights away from the family, missing birthdays, holidays, and other family events. Your first child walked while you where away, they hit the winning home run in the little league game, but you where not there.
I flew my first commercial flight in May 1971, First Officer in an Twin Otter, DHC-6. It was a 20 minute flight to Nantucket (ACK), I thought that I would never be able to keep up with such a fast airplane! Forty three years and four companies later, and I retired in Oct 2014, Captain 777.
Would I do it again, no question yes! It was not as great as I hoped it would be, but it is the great job yet!