Hmm, well: are shadows an _absence_ of light, or are they a _negation_ of light?
The question I find myself asking is, would positive emotions still be as rewarding if they could only be contrasted to the absence of emotion, or do they really require negative emotions to be brought into full relief? Because there are two kinds of polarity. Maybe absence of emotion provides enough contrast.
Of course, risk of loss is necessary to get the greatest gains. But maybe risks can be hedged if one is sophisticated enough?