This isnt really saying that life is always positive in the end result of the math. It's saying that the distance that life is from 0 is {insert value of life.} The number is no longer life. The number at the end of the math is the absolute value of life which is a totally different number entirely.
edit: the way one would have to do this to make it how the post intended is to do something code like such as
_
life = abs(life);
edit: the way one would have to do this to make it how the post intended is to do something code like such as
_
life = abs(life);