I don't think that is the school motto for Harvard University. Anyway, below is my version for your reference.
你所浪费的今天,是昨天死去的人奢望的明天；你所厌恶的现在,是未来的你回不去的曾经.
Today that you are wasting is the unattainable tomorrow to someone who expired yesterday. This very moment that you detest is the unreturnable experience to your future self.