Seems like an excuse to avoid negotiating because it makes you uncomfortable. Ironically, the life is too short argument is horrible in this context due to the fact that the amount of time you are forced to work while you live is dependent on the amount of money you make. If you can increase your salary by 10% by negotiating, the total amount of time you have to work in your life just decreased by 10%. Your next raise will also be 10% added to your salary that was already increased by 10%.