Social pressure is a pretty big motivator for most people. I find that customers are the big driver, if they're willing to wait (accept delays, don't bring the deadline in when it's been agreed) then I really feel no pressure at all to work overtime.
When the customer is screaming down the phone at your grand-boss that you've failed to deliver and they have very little context for that and ask you if you can work extra to make them happy you're in an awkward position.
The common thread is your boss, not your customer. A good boss is worth everything.
A good boss would push back on unreasonable customer demands and spend time figuring out what went wrong. A good boss will help prevent it from going wrong the next time. A good boss will help you figure out what needs to be done right now and what can be scheduled so it’s not just a constant “P1 emergency”
When the customer is screaming down the phone at your grand-boss that you've failed to deliver and they have very little context for that and ask you if you can work extra to make them happy you're in an awkward position.