Adding to my take on work...

Even the best person at work, one with a 'most valued employee' certificate, most efficient troubleshooter, extremely dependable person, 'indispensable' person etcetcetc.... is still, at the end of the day, dispensable. That is why it is so important that we don't allow the work, or these tags to define us, and instead define the work that we do with what we are all about. This is so that if you have to leave, for whatever reason, you would do so knowing that you had enjoyed the work while it lasted, and you have happy memories of what you gave to your work and your colleagues. You would be able to draw the line painlessly, and without bitterness, and quite naturally move into what came next, taking with you all that you had garnered...