Ambition should not be a product of hope but a product of well informed confidence. In other words if we chase down something based on what we hope will happen we are setting ourselves up to falter and fail.
This is not to say that ambition should not take chances, but the chance it does take should be one where we can control the outcome with our own skill and determination.
Ambition that rides on the back of luck and chance is like a child running with scissors, barefoot, in a room full of mousetraps. Sure they might make it safely across, but most likely there will be pain involved. When we are working to change our lives we cannot trust luck to carry the day.