I've spoken about the work/life balance before. It is so easy to fall into the trap of working continuously, squeezing just one more job in instead of stopping for lunch, going to one more call on the way home, setting out an hour earlier in the morning to beat the traffic, it all eats into your time. Perhaps I should capitalise: YOUR TIME.
Before you know it a 40-hour week has grown into a 50- or 60-hour week, you get more tired, you become less effective, more stressed, less able to deal with "difficult" customers -- and it's strange that, the more tired you get, the more "difficult" the customers are. Maybe the stress transmits from you to them without you realising. Stress can make you ill, it makes you more susceptible to viruses and reduces the effectiveness of your body's immune system.
So what's to be done? First thing to do is to remember that nobody ever got a medal for overworking. Secondly, if you upset too many customers your boss will consider getting rid of you. The most important person in the whole deal is YOU. The customer comes second after your personal health and sanity. Going the extra mile just wears your shoes out. The customer expectation needs to be managed properly. They should not expect you to drop everything and come running, they should expect you to arrive at the first possible opportunity but there is always the proviso that ‘possible' should be defined as the opportunity that presents itself once your own safety and comfort has been taken care of.
If you are fit and well and free of stress you will serve the customer better. Putting yourself first ultimately helps you to concentrate on the job in hand. Thinking clearly means that you get to the finishing post without having to go the extra mile. You will appear to be an expert, you will make the job look effortless and impress the client with your skill and expertise.
Remember, the worker is worthy of his hire. If you live and work in a culture where the time you arrive and leave comes under scrutiny maybe you should consider a move. If you are judged on your results and rewarded for them you will have the edge of keenness that you need to succeed. If you were recruited to work a 37-hour week, work a 37-hour week. Staying behind after work to get things finished hides the problem that you don't have enough time to do all the work expected of you. The problem with hiding problems is that nobody will know about them.