One of the chief reasons that destructive emotions like Lust , Greed, Hatred arise is that we are attatched to our current flow of life. We live with a sense that our life will last forever and we become fixated on materialistic things. To overcome this foolishness we need to reflect on the fact that a day is coming when we will not be there.
The maximum amount of time we might live will be around 100 years. No matter how many years we live ultimately we all die. And this can happen anytime. Just as time of birth can never be predicted, the time of death can never be predicted too. So no matter how rich we are, we can never take the money with us when we die. In this aspect the death of a rich person, poor person and animals is the same.
Even though there is no certainty we might die immediately, cultivating awareness of death makes us appreciate life even more. If we cultivate awareness of this, then we start focusing on emotions which brings out the goodness in us rather than destructive emotions which brings out anger, lust and hatred in us. Furthermore being aware about the uncertainty of life, we will refrain from doing something which does harm for the present and he future.
This awareness helps us in shaping our thoughts and actions which will be beneficial in the long run. By contrast if you start thinking that you will be permanent fixture in this universe , then you will start spending time on matters that is superficial which will be a great loss . So being aware that one will die will ensure that we enough good will during our temporary stay on mother earth