"Why do we strive so hard to live when we know we are going to die anyway?"
Maybe because most can't help believing that:
- our lives somehow have meaning and purpose - death can somehow be transcended
However, it would require someone who could just about walk on water to convince critical thinkers like ourselves that these beliefs might actually be grounded in reality rather than self-delusion.
Of course, another possible motivation is to outlive that mongrel across the road who keeps asking for his lawnmower back.