What does “Optimism keeps us moving forward rather than to the nearest ‘high-rise ledge’” mean?
Solution 1:
Suicides often jump from tall buildings: the "high-rise ledge" is a window ledge in a high-rise building, and the sentence is saying that optimism is what keeps us moving forward instead of killing ourselves.
There's a great phrase I first learned from John Irving's Hotel New Hampshire, and which later became a song by Queen: "Keep passing the open windows."
Solution 2:
I suspect the author was thinking of optimism and pessimism. Implying pessimism by suggesting suicide by reference to tall buildings amounts to hyperbole dressed up as euphemism.