Why some time we sad toward our life as we are aware of it?

Question

Why some time we sad toward our life as we are aware of it?

Answer 1

Because we lack the true awareness of it.

Answer 2

Because sometimes life sucks and it doesn't make sense to be happy.

Answer 3

Because with the awareness of life comes the awareness of mortality, and death is something we naturally fear.  But as they say, "Better to have lived and lost than to never have lived at all."  Actually I just came up with that.